Avos chapter 1, Mishnah 17. The Tanna before us is "Shimon his son" - Shimon ben Gamliel the First, son of the previous Tanna, Rabban Gamliel, and great-grandson of Hillel the Elder. Two Sages named Shimon ben Gamliel appear in the Mishnah, which can be confusing; here we are dealing with the first of them, who served as Nasi in the era of the destruction of the Beis HaMikdash. His tenure lasted close to twenty years and ended in approximately the year 3830 (70 CE), when he was among the Ten Martyrs killed by the Romans, and with that his role as Nasi came to an end.
The words of the Mishnah: "Shimon beno omer: kol yamai gadalti bein hachachamim" - Shimon his son says: all my days I have grown up among the Sages. There are two interesting points of precision here: first, he is not given the title "Rabban" in the Mishnah; second, he refers to himself as someone who is still growing and developing. Many of our commentators explain that this statement was made at an early stage, before he was appointed Nasi and while his father Rabban Gamliel was still alive, and that is why it is recorded without the honorific title. The rule is that the Mishnah does not budge from its place: once the wording of a statement has been fixed, it is not reformulated at a later stage, since that would be confusing and make it harder to remember, and so it remained as it was. The result is that even though he is already a Sage in his own right, he sees himself as one who is still growing - and so it is fitting for every person.
The Mishnah consists of three parts:
"Velo matzasi laguf tov ela shesikah" - there is nothing better for the body than silence.
"Velo hamidrash hu ha'ikar ela hama'aseh" - even in the context of Torah study, the learning is not the essence, but rather the deed.
"Vechol hamarbeh devarim meivi cheit" - one who talks a great deal and speaks excessively brings about sin.
The entire Mishnah, then, deals with the virtue of the trait of silence.
"Velo matzasi laguf tov ela shesikah":
The Tanna is speaking about the physical benefit of silence. When a person is angry and on the defensive, his blood pressure rises, and there is no benefit in that for his body. One who wishes to preserve his composure and his emotional equilibrium would do better to remain silent. The Bartenura explains that this is precisely the context of the Mishnah: it is speaking of a person standing in the face of humiliation or criticism, and even though accusations are being leveled at him or he is being shamed, he remains silent. That silence is for his own good and for his physical wellbeing.
This is familiar to everyone: from the moment a person responds, he becomes more and more heated and angry, and even if he is in the right, it makes no difference. He walks away from the confrontation unsettled, his appetite is affected, his sleep is disturbed, and he certainly cannot concentrate on his learning. It is a situation of loss from every direction, and he is the one who comes out the loser. Had he let the matter pass over him and ignored it, he would have kept his calm and composure, recovered more quickly, and gone on with his affairs.
It is worth being precise: silence is good for the body, but not for the soul. There is a mitzvah, and it is indeed proper, that one who learns Torah should articulate his learning aloud and actively, since verbalizing the words helps him to learn, to remember and to understand. It is only for the body that speech is of no benefit.
The foundation of these ideas is a verse in Mishlei: "Even a fool who keeps silent is considered wise; one who seals his lips is deemed understanding" - even a fool, if he stays silent, will be considered wise, and one who seals his lips is taken to be discerning. This idea became well known in modern times in a saying attributed to Mark Twain or to Abraham Lincoln, which my father would repeat constantly: better to remain silent and be suspected of being a fool than to open your mouth and remove all doubt. And the source of the idea is King Shlomo in Mishlei.
This is how the Bartenura and many others explain it: the Mishnah is dealing specifically with someone against whom things are being alleged, who is being embarrassed, or about whom lies are being told - and even then he should remain silent. And how much more so: if someone raises a valid point, offers legitimate criticism and points out a genuine shortcoming, certainly a person should stay silent and even accept the words - to be among those who love rebuke, and not to defend himself and quarrel, but rather to take it as something worth knowing and to grow from it.
The Rambam, in his Commentary on the Mishnah, understands the Mishnah in a way that is closer to the plain reading: it is not speaking specifically about someone who is being shamed, but about speech in general - that a person should speak less and gain from doing so. The Rambam takes the opportunity and lists, as he does in other places, the five levels of speech:
Forbidden speech: lashon hara, rechilus, a false oath and foul language. These things are forbidden in their very essence - falsehood, a false oath or a curse - and they certainly have no place.
Disgraceful speech: idle chatter. A person sits at the Shabbos table and talks about the food instead of about something loftier, or about who won a sports event. Such speech, in the Rambam's words, is lowly and disgraceful, and in that same time one could have been doing far better things.
Permitted speech: speech that is necessary for a person's physical and financial welfare, for the needs of his work and the like. When there is a need to speak - he speaks, and what is necessary is necessary.
Beloved speech: speech through which a person makes another feel good, encourages him, draws out the best in him and strengthens him to be a better person and to do good.
Obligatory speech: Torah study, Kerias Shema and the like - speech that is itself a mitzvah.
Through this hierarchy the Rambam points to the direction a person must take: to distance himself from the lower levels and to focus on the higher ones.
On this same theme there is a well known and unforgettable Gemara in Maseches Megillah (19a): "Darash Rabbi Yehudah ish Kfar Gibor Chayil: mah dichtiv - 'Lecha dumiyah tehillah'" - Rabbi Yehudah of Kfar Gibor Chayil expounded the verse "To You silence is praise" (a verse in Tehillim that has become well known in our times through Ishay Ribo's song, "Tze'akah Bat"). And what does the verse mean? "Samma d'chula mashtuka" - the remedy that helps for everything is silence, just as the Tanna teaches in our Mishnah. The Gemara continues: "Ki asa Rav Dimi amar, amrei b'ma'arava" - in Eretz Yisrael they say: "Milah b'sela, mashtuka bitrein" - a word is worth one sela coin, and silence is worth two. Silence is always preferable, unless a person has something worth saying.
"V'lo hamidrash hu ha'ikar ela hama'aseh":
In the second part of the Mishnah, Shimon his son teaches that even in the context of Torah study, where speech is a mitzvah, the study is not the main thing but rather the deed - actual practice. The source of this is the verse in Devarim: "And you shall learn them and guard them to do them" - a person learns Torah, but he must make sure that his learning is for the sake of doing.
In truth, this is a dispute discussed in the Gemara. In Kiddushin there is a famous discussion about which is greater and which comes first - study or action: "Rabbi Tarfon and the elders were once reclining in the upper story of the house of Nitzah in Lod," and the students posed the question before them: is study greater or is action greater?
Rabbi Tarfon: "Action is greater" - the deed is primary and takes precedence over study.
Rabbi Akiva: "Study is greater" - learning is greater than action.
In the end they all concluded: "Study is greater, for study brings one to action" - learning is the greater one, because it is what brings a person to action. The understanding behind this is that if a person increases his deeds, that will not lead him to learn more; but if he increases his learning, that will lead him to do more.
The Gemara itself requires explanation, since the question as such is puzzling: among the 613 mitzvos, one of them is Torah study, and it is a mitzvah in its own right. In any case, the point of our Mishnah is that the Tanna takes a side in this discussion and establishes: as important as study is - or in his language here, "the midrash" - the main thing in the end is the deed, applying what has been learned in practice.
"V'chol hamarbeh devarim meivi cheit":
In the third part, after we have learned how proper it is to avoid an abundance of words, we enter a further stage: if a person is already about to speak, at the very least he should keep his words to a minimum. This is almost a situation of bedieved - the more a person says, the worse his position. Chazal said, "Whoever adds, detracts" - the addition itself takes away from the matter. And as is well known, when a person sits giving testimony or under investigation, anything he says is liable to be used against him; the less he says, and the more directly and briefly he answers the questions - the better off he is.
The illustration Chazal bring for this is the story of Chavah. The Holy One commanded Adam and Chavah not to eat from the tree, and when the snake spoke with her she added and said that not only were they forbidden to eat from the tree, but even to touch it. Those extra words are what led her to sin, for they made it possible to deceive her: it is not touching the tree that causes death, but only eating from it. From here we learn that a person must focus on the importance of precisely this point - to maintain clarity between what is d'Oraisa and what is d'Rabbanan, and to understand the distinction properly.
And as a general rule: the more a person talks, the more likely he is to get worked up, to say things that should not be said, to feel badly about himself and about others, to stumble in lashon hara, and so on. He should therefore try to stop the words while they are still budding, and speak as little as he can.
Rabbeinu Yonah adds that since the previous part of the Mishnah dealt with Torah study, this part too refers to Torah study. He cites the words of the Gemara in Chullin (63): "Le'olam yishneh adam letalmidav derech ketzarah" - a person should always teach his students in a concise way. One must teach his students briefly, with few words and with maximum clarity, all for the sake of the student's understanding. The point is that when a person adds, he subtracts: he says more, and in fact says less, because he adds confusion instead of weighing each word and clarifying it from the very first time, so that no misunderstandings remain and the transmission of Torah is entirely clear.
In summary: in this Mishnah we learned three principles from Shimon ben Gamliel: there is nothing better for the body than silence, especially in the face of criticism and humiliation; it is not the study that is essential but the deed, and Torah learning is directed toward action; and whoever multiplies words brings sin, and one should therefore limit his speech and speak in a brief and clear manner.