Chapter 10 of Kohelet opens with a verse that appears short and simple, but actually contains profound foundational principles: a rule of Hebrew grammar that illuminates many verses throughout Tanach, a principle regarding the severity of sin measured by the stature of the one who commits it, and a powerful insight from the Malbim on the distinction between an intrinsic acquisition and an incidental one. Let us proceed step by step, and see how a single tiny fly can teach us about a person's entire spiritual life.
זְבוּבֵי מָוֶת יַבְאִישׁ יַבִּיעַ שֶׁמֶן רוֹקֵחַ, יָקָר מֵחָכְמָה מִכָּבוֹד סִכְלוּת מְעָט. - Dead flies make the perfumer's oil putrefy and ferment; so does a little folly outweigh wisdom and honor.
Before examining the literal meaning of the verse, let us address a grammatical point that is also crucial for understanding many other verses. The text states zvuvai mavet yav'ish yabi'a - and this is puzzling: it should either say zvuvai mavet yav'ishu yabi'u (plural), or zvuv mavet yav'ish (singular). One does not say zvuvai (plural) followed by yav'ish (singular). The Ibn Ezra explains a fundamental principle: the verse begins with a general group - there are multiple flies - and then narrows down to the individual, teaching that each and every one of them will putrefy and ferment the perfumer's oil. The singular verb refers back to every individual element within the collective.
According to this principle, many verses are resolved. Banos tza'adah alei shur ("Daughters stepped over the wall") - not tza'adu (plural), but rather each individual daughter stepped, each in her own place. "And the woman took the two men and hid him" (vatitzpeno, singular) regarding the spies sent by Yehoshua - the Ibn Ezra notes: it does not say vatitzpenem (plural), but rather she hid each one in his own spot; this one she hid here, and that one she hid there. (As noted in the study of the Prophets, Pinchas did not need to be hidden at all because Pinchas is an angel, but this is the plain meaning of the text according to the Ibn Ezra.) Similarly, "And Chizkiyahu took the letters and read it" (vayikra'ehu) - and not vayikra'em (plural) - because he read each one individually: he read this letter, and then that letter. Thus, it is entirely fitting to begin in the plural and continue in the singular when the verse focuses on the particulars.
The Ibn Ezra continues and explains: dead flies spoil the perfumer's oil, and similarly, a person who is "precious" (yakar) from wisdom and honor - where yakar also connotes heavy, as in "Pharaoh's heart grew heavy" (vayichbad), which Targum renders ve'itikar - someone endowed with wisdom and honor, if he possesses even a little folly, it ruins his reputation and defames him. Just as a tiny fly ruins a large quantity of fine oil, so too is a small amount of folly heavier than wisdom and honor. If you place both on the scales, the little folly will tip the balance against the honor and wisdom on the other side.
And what folly is this referring to? The Ibn Ezra explains: this folly is sin. This connects directly to the conclusion of the previous chapter: "and one sinner destroys much good." Even a single sin committed by a wise person is grave; it carries immense weight.
The Ibn Ezra brings an example: consider Shlomo HaMelech, to whom Hashem appeared twice, who was granted divine revelation, built the Temple for the honor of Hashem, and whose wisdom surpassed all earlier and later generations, with no injustice found in him. Yet because of a single sin - that he did not scrutinize what his wives were doing, and they built shrines for their gods using Shlomo's wealth - the verses use severe expressions against him. All because of what? See how a little folly outweighed vast wisdom and honor.
Do not wonder at this, for here lies a crucial principle: every sin is considered small or great according to the stature of the one who commits it. The gravity of a sin is not measured in the act alone, but in relation to the individual. For one person, the slightest misstep may be judged as immensely severe, while conversely, for a lowly individual, even a grave sin may not be viewed as so severe, because he is foolish and lacks understanding, and thus the act is weighed accordingly. This reflects the principle of "Through those near to Me I will be sanctified," and as our Sages so profoundly expounded on the verse "and around Him it storms exceedingly" (u'sevivav nis'arah me'od) - that the Holy One, Blessed be He, is exacting with the righteous down to a hairsbreadth.
And likewise, harsh words were written about figures even greater than King Solomon, concerning slight matters that were not done intentionally, but because the outcome came about through them, they were held accountable as if for great sins. As it is written regarding Moshe Rabbeinu, "Because you did not believe in Me" - as though he was held to account for a lack of faith. And what was actually there? A sin that the commentators wearied themselves to identify: the holy Or HaChaim brings ten explanations and refutes them all. We see how difficult it is to pinpoint a sin in such great individuals, and yet - come and see how a little folly outweighs wisdom and honor, just as a tiny fly spoils a large quantity of fragrant, perfumed oil.
The Gemara in Berachot (61a) states: Rav said, the yetzer hara is like a fly, as it says, "Dead flies make the perfumer's oil stink and ferment." The parable is remarkably precise: one never defeats the yetzer hara once and for all, just like a fly. No matter how much you shoo it away - it keeps coming back. It is as if the fly says: look how happy they are when I arrive; every time I show up, they applaud me right away.
They tell of the Chazon Ish that when they were sitting and learning, there was a bothersome fly, and his study partner kept trying to shoo it away. At a certain point, the Chazon Ish said to him: Leave it be, "a Rosh Hashanah fly" - this is a fly decreed upon us on Rosh Hashanah that we should suffer from it. If it was decreed that we should suffer, then we will suffer. And that is precisely the struggle with a fly: it always returns, it never lets up. In the same way, the yetzer hara never despairs. It is "dead flies" (zevuvim of death) - a fly that seeks to bring a person all the way to death, and it does not rest until the final shovel of dirt.
Ben Azzai expounded: "Dead flies make the perfumer's oil stink and ferment," juxtaposed with "and one sinner destroys much good." This teaches you: when a single fly dies, does it not spoil and ruin the perfumed oil? Could you think that one fly is not enough? So too, through a single sin that one commits, he loses all the merits he possessed. And which sin is meant? When he regrets his former good deeds (toheh al harishonot) - through this, he erases all the earlier ones. This is cited by the Yerushalmi in Kiddushin (Chapter 1, Halachah 9).
Chazal also apply this verse homiletically to historical figures, explaining that yabbia (ferments) is related to expressing words, speech that flows forth (nove'a). Another explanation: "Dead flies make the perfumer's oil stink and ferment" - this speaks of the assembly of Korach. Yesterday they brought a foul stench against Moshe, saying, "Moshe is not a true prophet and Aharon is not a Kohen Gadol" - that is yav'ish (makes it stink). And today, yabbia - they utter words before Moshe, saying, "Moshe is a true prophet, Aharon is the Kohen Gadol, and the Torah is from Heaven." After they received their blow, a different tune comes out of their mouths.
Another explanation: It speaks of Doeg and Achitophel. Yesterday they uttered foul words against David, saying, "He has a tainted lineage - before you ask whether he is fit for royalty, ask whether he is even eligible to enter the congregation of Israel." And today, after their death, they express words of shame and regret over their deeds. Another explanation: It speaks of the generation of Eliyahu. Yesterday they uttered foul words against him, shouting, "O Baal, answer us," and calling him a false prophet, and today they express words, crying out, "Hashem, He is God!" - full of remorse, singing a completely different tune.
The Pesikta Zutreta notes: If flies fall and die in the perfumed oil of kings, it makes it stink and ferment (yav'ish yabbia), where yabbia is related to "a breach (niv'eh) in a high wall," meaning it ruins it. Notice the precision: even oil into which a fly has fallen and spoiled it slightly, though it is no longer fit for kings, is still precious oil, suitable for ministers and dignitaries. But when it comes to the wisdom and honor a person possessed, a little folly destroys them completely. The oil descends in status yet retains some worth, whereas the wise man - a little folly can bring him down entirely, as it is written, "and one sinner destroys much good."
What is the meaning of "dead flies" (zvuvei mavet)? One might think this refers to a specific species of fly. Rashi explains: "Dead flies" - such as in the days of winter, when flies have no strength and are close to dying. That is, a weak, dying fly for whom flight is difficult. And yet, if it falls into perfumer's oil and mixes into the spices, which are exquisite things, it makes it putrid.
And what does yabia mean? Rashi explains: yabia means it brings up froth, called escuma in Old French, and bubbles appear in it. When something spoils, fermentation and froth begin - like wine that goes bad, where bubbles and foam are seen on top. And this is the wonder of it: a dying fly, so weak and powerless, succeeded in ruining precious and exquisite oil. Rashi comments: imagine a person whose sins and merits are balanced equally, and he commits one sin - it tips him to the scale of guilt. A little folly, a small sin, is "precious" - meaning heavier and carrying more weight than all the wisdom and honor within him, and it is what tips the entire scale.
Chazal also expound: The evil inclination resembles dead flies, and it spoils a good name - for "better is a good name than good oil," and a good name is superior to good oil. "Perfumer's oil" here refers to a person's good name, and when an evil report comes out about him, it overpowers his good name. This reflects reality: for a person to acquire a good name takes years of toil - years of decency, reliability, and uprightness. In contrast, if someone spreads some small rumor about him, it sticks immediately. People instantly say: "What was said is true; it certainly looks that way, and the circumstances prove it." A bad name sticks to a person easily, whereas with a good name, people wonder: who says he is truly decent? How can we know? Perhaps after many years he will establish a reputation. It is deeply frustrating: someone fabricates a petty story about him, and that alone is enough for the fragrant oil - his good name - to be spoiled and ruined by a tiny fly.
Chazal also expound this concept in relation to Torah. In Shir HaShirim Rabbah: Why are words of Torah compared to oil? Just as with oil, when a little water enters it, the oil overflows and is lost, so too with words of Torah: when a little levity enters, much Torah is lost. The explanation is simple: any liquid you pour into another liquid blends with it. If you pour water into wine, when you pour it out, wine and water emerge together. If you pour water into juice, juice and water emerge together. But with oil it is not so: pour water into oil, and because the water is heavy, it immediately sinks to the bottom, while the oil is light and floats to the top. What spills out first is only pure oil, without mixture, while the water remains below. This is what the Midrash conveys: words of Torah are compared to oil, and when a little levity enters them, the Torah is what gets lost first. "And one sinner destroys much good" - do not read "good" (tovah), but rather "Torah".
There is a remarkable explanation here from the Malbim, and reading it on this verse only deepens the regret that we were not privileged to have his commentary on the entire Book of Kohelet. This teaching appears in his work Artzot HaChaim, in the essay Afsei Aretz, page 25, Derush 1. There, the author presents a full discourse on another topic, and weaves into it an exposition of our verse, granting us his insight into at least this verse of Kohelet. There are other such verses that he explained in passing elsewhere, and we endeavor to bring all of them according to the biblical order.
The Malbim explains: A person who delves into wisdom out of a love for wisdom is called a lover of wisdom, a seeker of wisdom. But one who delves into wisdom for a different objective - wealth or honor - is not called one who delves into wisdom, but rather a seeker of wealth or a pursuer of honor, because a person's path is defined by his ultimate purpose. If someone sits and studies in order to attain rabbinic judicial ordination (dayanut) and secure a judge's salary, what is the real purpose of all his current effort? He is like a law student whose goal is simply how to make money; otherwise, he might just as well study something frivolous. One who seeks wisdom where the ultimate goal is money is called a seeker of wealth, "since these are the ultimate ends of his study and the purpose of his intention."
And should your heart ask: What does it matter whether he is called a seeker of wisdom or a seeker of wealth and honor? In the end, he immersed in Torah, toiled in it, diligently pursued wisdom, and it entered his being like water! What difference does it make whether someone was looking for a lost pearl in the sand, or searching for ordinary pebbles and happened upon a pearl? In the final analysis, what did he find? A pearl! If so, why view this so negatively?
To this the Malbim replies: Incline your ear and hear the words of the philosopher - the deep thinker. "An essential acquisition is unaffected by chance occurrences, whereas an accidental acquisition is affected by chance and its like." In plain terms: something that is an essential acquisition cannot be harmed by external incidents. In contrast, something that is merely an incidental acquisition, acquired only as a byproduct, can easily be damaged and altered by external circumstances.
The Malbim provides a wonderful example from physical reality. There is fire, and there is hot water. What is the difference? Fire - its heat is intrinsic. Water - its heat is incidental; it received it from the fire. Fire receives heat from no one. In his words: its intrinsic heat will not cool from the cold, nor will it freeze from frost and snow; on the contrary, they will melt and vanish in its heat. Can anyone freeze fire? Never. At most, it will melt the ice and snow. But hot water - its heat is incidental to it, an accompaniment, and therefore "they are affected by ice to become cold, and cast forth ice like morsels." Cool them down, and they freeze. No one has ever managed to freeze fire, but water, yes. This is intrinsic heat, and that is incidental heat.
And so, the Malbim explains, myrrh and persimmon oil - their fragrance is intrinsic. They did not acquire their scent from another source. Therefore, they do not rot from putrefying flies, nor from any foul odor placed in them; on the contrary, they transform it into an enduring pleasant scent. And do you wish to see to what extent? Consider the embalming practiced in ancient times: they would take a corpse, which naturally decomposes and should foul the oil upon it, and apply these types of oils whose fragrance is natural to them - and they overpowered the smell of the corpse and imparted a sweet aroma to it. This is not the case with apothecary oil: this is ordinary oil into which various spices have been compounded, boiled into it - merkachat being related to cooking. Its scent is not intrinsic, but incidentally acquired. Therefore, "Dying flies make apothecary oil foul and ferment" specifically - the flies' entire power is only over apothecary oil, not over persimmon oil and oil of myrrh, whose fragrance is intrinsic. That which has an intrinsic fragrance cannot be nullified. That whose fragrance is acquired and incidentally attached - dying flies will come and foul it.
Thus far the mashal, and now to the nimshal. So it is with the acquisition of wisdom: one who has acquired the study of wisdom such that wisdom is intrinsic to him, turning toward no external purpose, nor toward the arrogant pride and desires of the era - who did not acquire wisdom to earn a degree or gain wealth - "his taste remains in him, and his scent is not altered" by any circumstance. The flavor will always remain within him, for the acquisition of wisdom is intrinsic to him, like fire whose heat is intrinsic and like persimmon oil whose fragrance is intrinsic. And none of the myriad circumstances crowding together "to turn wise men backward and make the counsel of the prudent foolish" will overpower him.
However, one whose acquisition of wisdom came to him incidentally - through the love of honor and desire for wealth, which are what brought him to the house of study, and amid the pearls of wisdom he seeks the earthen shards of transient vanities, his entire aim being how to make money, how to acquire fame and honor, how to obtain a degree - when such a person encounters the myriad circumstances that bend the bow, shoot arrows, and make him a target to abuse as they see fit, meaning when trials and hardships arise, he will become enraged, banish wisdom from his territory, and overturn the bowl completely. Because wisdom is incidental to him, the moment opposition arises, he will cast wisdom aside. But for one whose wisdom is an intrinsic acquisition, this will not happen; on the contrary, when adversaries arise, he will prevail over them, for an intrinsic acquisition cannot be nullified, like fire whose heat is intrinsic to it.
A person once asked about a certain place of study - its name will not be mentioned - a place where, instead of a standard Yeshiva Ketana and against the guidance of the Gedolei Yisrael, they teach various secular subjects and prepare for matriculation exams, alongside high-level Gemara study. It is indeed considered a high-level institution; young men from such places arrived at yeshivas like Chevron who were at a high level in their learning. He wanted to send his son there, and another person asked on a different occasion regarding a shidduch. The answer given to them was: having studied alongside such individuals for a long time, both in yeshiva and later in kollel, one thing was striking, and later it became clear that this is exactly what the Malbim is explaining here.
There was a brilliant fellow in kollel, sharp-minded and a great lamdan. Indeed, in terms of diligence and seriousness, such students often outdo those from traditional yeshivas - a student-like drive, rigorous standards, pursuing degrees. Then one day, people arrived at the kollel and he was not there. When asking what happened, the answer was: he switched to high-tech. The speed with which he cut ties was unforgettable. He studied a bit of programming in the evenings, and they snapped him up. In a single day, from being a kollel avrech - and not one who merely warmed the bench, but one who learned seriously. And this was not just one or two individuals; one could see how quickly they switch gears. By contrast, a young man who learned in a Yeshiva Ketana, with the shmuessen of a mashgiach and exclusively kodesh studies - that is something entirely different. Even if one observes a decline in his case, it is a gradual descent, not an abrupt break. The problem is that the style of learning there is academic: summarizing everything, reviewing the material, all fine and good - but just like at university, the moment a better salary and a better position come along, he leaves. It is heartbreaking, but that is the reality. And it all hinges on one question: did the acquisition of wisdom come to him incidentally, or is it intrinsic to him? For one to whom wisdom is incidental, "myriad circumstances that shoot with bows will find him," and he will promptly "become enraged, banish wisdom from his territory, and overturn the bowl completely." Here lies a way to make money faster and easier, without all this intense study.
And there was already an individual who became a Member of Knesset, and subsequently even disputed his own rabbeim: Rav Ovadia Yosef is worth nothing, Rav Mazuz is nothing, each of them dismissed. And he goes from place to place for what purpose? To scavenge votes at the expense of his Torah- and mitzvah-observant brethren, claiming that they do not understand enough, and that he knows how to accept converts even when there is no genuine intention to observe Torah and mitzvot. He wrote a lengthy responsum, indifferent to the fact that Rav Ovadia Yosef stated that he was writing nonsense and that this was incorrect, and even instructed his son to fight against all such approaches - Rav Yitzchak Yosef spoke publicly about this, explaining that his father's final directive was to battle against those who bring non-Jews into the vineyard of the House of Israel when they have no genuine intention of converting. He brought all kinds of far-fetched arguments and convoluted logic, all directed against the Gedolei HaDor. Does one dispute Rav Elyashiv, Rav Ovadia Yosef, Rav Nissim Karelitz, Rav Mazuz, one's own rebbe? What was discovered in the Torah that they did not know? It is astonishing. But when a person studies in an academic manner, and the goal of study is the attainment of authority and prestige, and if he believes that as a Member of Knesset he will achieve more authority and honor - he will sell out everyone, sell out the Torah, sell out everything. For that was the ultimate goal. One to whom wisdom is incidental casts everything aside with ease. But one to whom wisdom is intrinsic - his scent and taste will never alter due to any of the myriad circumstances crowding together to turn wise men backward and make the counsel of the prudent foolish.
From here, explains the Malbim, we can understand the verse: just as dying flies foul and ferment apothecary oil - oil that is compounded and spiced with aromatics, whose scent is incidental because it merely absorbed it from the spices, unlike oil of myrrh whose fragrance is intrinsic and unaffected by flies - so too the continuation of the verse. Yet the phrasing is difficult: "More weighty than wisdom, than honor, is a little folly" (yakar meichochmah mikavod sichlut me'at). It should have said "than wisdom and honor" (meichochmah umikavod)! What then is "from wisdom, from honor"? Rather, the Malbim explains with precision, there is no mistake here: it refers to wisdom that comes from honor. Wisdom that one labored over for the sake of honor, wisdom whose entire purpose and origin stemmed from honor - wisdom acquired incidentally through the love of honor, which is what is truly intrinsic to him. Concerning such wisdom it is said: "A little folly is weightier" - a little foolishness tips the scales, and a little folly arrives and "his wisdom flies away like a bird." All of his wisdom takes flight in an instant. Why? Because this is wisdom derived from honor, not wisdom born of a true striving for and genuine attainment of wisdom itself.
According to this, the Rav explains, we can sometimes rightfully say something surprising. Imagine two people parting ways from one another: one goes to market day for commerce, and the other goes to the Beit Midrash to engage in wisdom. Yet we could say that the first went to the market to engage in wisdom, while the second went to the Beit Midrash to engage in commerce. Have we turned things upside down? Rather, the Rav says: "If one looks at the goal of their actions and the ultimate intent of their purpose." If you truly examine the ultimate purpose for which they went, you will realize that the one who went to the Beit Midrash actually went to the market, and the one who went to the market actually went to the Beit Midrash.
For if the first goes to engage in business to provide sustenance for his household so that he may engage in Torah - that is his entire objective. When Hillel went to work and earn a half-dinar (a tarpeik) - would you say that Hillel was a businessman, seeing him go to the marketplace? It is obvious to all of us that this is not his definition, even though outwardly it might appear so. He went to the market, yes, but he earned a tarpeik in order to reach the Beit Midrash. The Rav then writes: "That very commercial pursuit itself becomes an engagement in Torah." In Heaven, that time he spent doing business is credited to him as Torah study, because its sole aim was Torah study. Torah is the true acquisition here. "For the means that lead to the objective are themselves considered part of the thing they facilitate."
We have previously explained why in Christianity they say that the end justifies the means, whereas in Judaism, Heaven forbid - the exact opposite is true, and this is expressed in countless examples. The end does not justify the means; even if your goal is holy, the means must be holy as well. If you achieve a holy goal through unholy means, you defeat the purpose entirely. Suppose someone wants to bring people to repentance through fabricated stories - and there are those who make an entire enterprise out of this, standing up and recounting things that never happened. As Rabbi Eliyahu Rabi says: "A story that almost happened" - and sometimes it did not even almost happen, it was never anywhere close. A lecturer once stood up to speak and said: "Know that I may tell you many stories that never happened, but do not be surprised, for I asked the Rabbi and he told me that to bring Jews closer, one may even tell stories that never occurred." And then he added: "And that is the first story."
There is no such thing, gentlemen. Truth is conveyed through truth; one cannot sell truth with falsehood. This is why Hashem hates robbery in a burnt offering - if you bring an olah, it must be the pinnacle of holiness and purity, otherwise Hashem says, "To what purpose is the multitude of your sacrifices to Me?" - I have no desire for it. One who fulfills the mitzvah of taking the lulav with a stolen lulav or a stolen etrog has committed a sin rather than a mitzvah: "And the robber who blesses blasphemes Hashem." In the secular worldview of the nations, the end is all that matters; in Judaism, the means are an integral part of the goal. That is what the Rav emphasizes here: "For the means that lead to the objective are themselves considered part of the thing they facilitate."
Let us consider an example: one person toiled for four hours in the scorching heat, searching on market day until finding a beautiful, choice etrog; another person found a beautiful, choice etrog in an instant. Both fulfilled the mitzvah - will they receive the same reward? Certainly not. If we looked only at the final result, perhaps the second person would receive a greater reward, since his etrog was more choice, and acquired effortlessly. But we do not look only at the end result: the means are considered part of the mitzvah, and one receives reward for them just as for the mitzvah itself. Indeed, there are sources indicating that the preparation for a mitzvah is even more precious and significant than the mitzvah itself - a topic discussed at length previously, but to give a hint: kindling the Menorah is valid when performed by a non-Kohen (a zar), whereas cleaning and preparing the Menorah (hatavat ha-nerot) can only be done by a Kohen! The preparation for the mitzvah is so precious that it exceeds the mitzvah itself; this is discussed extensively in Chassidic thought. We thus learn that the means are not merely a prerequisite for the mitzvah (hechsher mitzvah), but part of the mitzvah itself. Therefore, one who goes to do business in the marketplace with the goal of studying Torah - that business activity itself is considered as Torah study for him.
The Rav adds an analogy: just as one who treads clay and kneads straw in the mire is regarded. You see a person treading in clay and mud, and what is he doing? Preparing mortar for construction. Would you tell him, "You are merely playing in mud?" No, sir; what is the purpose? From the clay he makes bricks, and from the bricks he builds a house; therefore, he is considered to be engaged in building. Likewise, one who engages in business for the sake of his Torah study is considered, during that very business activity, to be engaged in Torah.
This is what the Sages meant when they said: "Torah study is good together with derech eretz (worldly occupation), for the toil of both makes sin forgotten." The commentators, such as the Tosafot Yeshanim in Yoma 85b, note that this is astonishing. After all, nothing is more precious than the Torah. By the way, there are phrases one should never use, such as "the Holy One, blessed be He, and..." - the Holy One, blessed be He, can never be coupled on an equal footing with anything else. Torah is the most precious thing: "The Holy One, blessed be He, the Torah, and Israel are one." How, then, can one say "Torah and derech eretz, the toil of both"? You are pairing Torah with derech eretz, which is an engagement in earthly matters, mentioning them in the same breath, making it seem as though Torah were secondary or merely equivalent?
Rather, the Rav explains, according to what we have written, the teaching comes to instruct you: even when you are engaged in labor, if your ultimate intent is to enable yourself to engage in wisdom, then while engaged in derech eretz it is considered as if you are engaged in Torah. It shields you from sin just as when you are literally studying Torah. When you engage in derech eretz with Torah as your aim, that labor possesses the protective power of Torah - aguni meganna (it shields and protects) over one's mundane work.
This was explained at length in the shiurim on Nefesh HaChaim, where the Rav expounds on the phrase, "Conduct yourself in them with the way of the world (derech eretz)." What is meant by "in them"? Conduct the words of Torah within worldly affairs - that is, whenever you engage in any matter of worldly occupation, let it all be bound up with the Torah.
People used to know Tehillim by heart, and in the midst of their work they would complete the entire Book of Tehillim - even simple folk, in Iraq, Yemen, and Morocco. They would walk about reciting Tehillim constantly, reviewing and repeating Mishnayot. It is told of the Steipler that he was handy with his hands and knew how to fix things; he had chairs at home that he would repair every so often - buy new ones? Out of the question! He would take a hammer, nails, and glue, and fix them, and all the while he was seen murmuring Mishnayot. The chair needs fixing - true, but "conduct yourself with them in the way of the world": while occupied with words of Torah, attend to what you need for everyday practical affairs.
And that is why we explained previously that the Gedolim did not choose occupations corresponding to their lofty stature, but rather simple crafts: Rabbi Yochanan was a shoemaker, Rabbi Yitzchak was a blacksmith, Hillel was a woodchopper and porter. And why did they choose such simple trades? Each of them was a towering genius, and they could have been given professions involving complex accounting and matters requiring calculations, trades in which kings take pride. Rather, they did not want occupations that consume the mind. All the trades they chose were crafts that leave the mind free: you drive nails and do not require intense mental effort; you can contemplate Torah thoughts while hammering nails - just being careful not to hit your finger. One can be a blacksmith and meditate on Torah. But a profession that demands calculations already occupies the mind, and would one surrender his mind to that, when during that time he could be meditating on Torah?
A single verse, "Dead flies make the perfumer's oil ferment and rot; so a little folly outweighs wisdom and honor" - and within it lies an entire world. We learned the scriptural method of opening with a general principle and descending into detail; we learned from the Ibn Ezra and from Rashi that a little folly - a single sin - is heavier and outweighs an entire lifetime of wisdom and honor, and that the gravity of a sin is measured according to the stature of the one who commits it; we saw that the Yetzer Hara is like a fly that never gives up, and that "one sinner destroys much good," and that a good name is built over years and destroyed in an instant. And the Malbim added the great principle: an intrinsic acquisition is not affected by external happenstance, while that which is incidental is nullified by any chance occurrence. Wisdom acquired for the sake of honor or wealth is like perfumed oil whose fragrance is merely added, and a tiny fly rots it; wisdom acquired out of love for wisdom itself is like fire whose heat is intrinsic, and like pure myrrh oil whose fragrance is intrinsic, and no external event can extinguish it. From here comes the practical conclusion as well: everything follows the ultimate purpose, the means are part of the goal, and for one whose entire aspiration is Torah - even his hours in the marketplace and at work are reckoned as Torah for him.