Chapter 3, Mishnah 3. The Mishnah continues discussing the halachic definition of an act of eating. In the previous Mishnah, we learned that one must eat the measure of a kezayis, and that if the measure is divided into two half-zaysim - they both combine with one another, provided they are eaten within the required time frame. Our Mishnah comes to clarify what that required time frame is, and there are two opinions on this question.
The opinion of Rabbi Meir:
The time limit: The time frame in which eating a kezayis is measured is the time that would be required to eat a kezayis that was crumbled into tiny pieces the size of kernels, kelayos (roasted grain kernels), when eating them one by one - similar to eating sunflower seeds, seed after seed. Even though the total volume eaten is only a kezayis, eating kernel after kernel takes a much longer time.
Continuous eating: A person who eats in one long, continuous session - putting food into his mouth, chewing, swallowing, and repeating - is performing a single act of eating, even if it lasts a very long time. A person might eat continuously for a full hour, and as long as he did not stop, everything combines together. Therefore, if he ate a kezayis of chelev within that hour and did not stop at all, he is liable.
The opinion of the Sages:
According to the Sages, the kezayis must be eaten within the time limit called "k'dei achilas peras", which is a fixed time frame - let us say three minutes for now. If he did not eat within this time frame, it makes no difference that he ate completely continuously, chewing and swallowing without a moment's pause: once he exceeded the time frame, the eating lasted too long and he is exempt. The measure of "k'dei achilas peras" is slightly shorter than the time required to eat a kezayis of kelayos kernel after kernel. Thus, the Sages are more stringent than Rabbi Meir regarding the duration of time, and more lenient than him in that a pause in the middle does not necessarily invalidate the eating.
What is a "peras"?
The word "peras" is related to the word "perusah", which means a broken piece, and it refers to half a loaf of bread. This measure is defined in Tractate Eruvin regarding the laws of eruvei chatzeiros: the amount of bread a person eats in a day is his daily food ration, the main source of his satiety, alongside the other accompanying foods. In the time of the Mishnah, a person ate two meals a day - a morning meal and an afternoon meal - one meal being half the loaf and the second meal being its second half. That half is the "peras".
What is the volume of that loaf? The Amoraim, and subsequently the Rishonim, disagreed on this question: is the entire loaf a volume of eight eggs or a volume of six eggs? Rashi maintains it is eight eggs, and the Rambam maintains it is six eggs. Since the peras is half the loaf, according to Rashi the peras is a volume of four eggs, and according to the Rambam it is a volume of three eggs. Meaning, the time in question is the time required to eat bread the volume of three or four eggs. The poskim established a broad range, from a minimum of two minutes up to nine minutes, but in practice, in most cases it refers to three or four minutes as the measure of "k'dei achilas peras".
It emerges that the dispute revolves around two aspects: the length of the time limit - the time to eat a kezayis of kelayos piece after piece for Rabbi Meir, as opposed to the time to eat half a loaf of bread for the Sages; and the law regarding pausing - that for Rabbi Meir, continuous eating combines even over a long period, whereas for the Sages, the fixed time frame is what determines it.
The text of the Mishnah:
The Mishnah asks how much time may pass between eating the first half-kezayis and the second half-kezayis for them to be considered a single act of eating, so that the two half-zaysim combine to make the person liable, for example, for a chatas offering for eating chelev. To this Rabbi Meir says: "K'ilu hu ochel kelayos" - the time limit is measured by eating in small pieces, and therefore it lasts a long time, piece after piece. The Bartenura explains that "k'ilu" means "like", and it comes to add that even one who eats in one long sitting is liable. And the Sages say: "Ad sheyishheh mitechilah v'ad sof k'dei achilas peras" - this is the amount of time it takes to eat a peras, half a loaf, from beginning to end. Meaning, he has only three minutes at his disposal to eat the two half-zaysim, and if he did not eat them within that time, it is not a single act of eating and he is not liable.
The halachah:
The halachah follows the view of the Sages, that one must eat a k'zayis within the time of k'dei achilas p'ras - a volume of at least one olive within the time required to eat half a loaf of bread, which is generally three or four minutes. This law applies to all halachic eating. Therefore, regarding eating matzah at the Pesach seder, which is a mitzvah, one must eat the entire k'zayis within k'dei achilas p'ras. Again, sometimes this refers to a short time span of just two minutes, but in most cases it refers to three or four minutes for eating the matzah.
A practical application:
Let us picture a scenario: There is a giant French baguette before us, and a thin layer of chelev, in the exact volume of just one k'zayis, is spread across the entire thing. A person devours the baguette continuously, like in an eating contest, and due to its size, the eating takes fifteen minutes even though he ate with full vigor. According to Rabbi Meir, since he ate a k'zayis of chelev in one continuous eating, he is liable. According to the Sages, however, he is not liable: Since it is impossible to eat this baguette any faster, and it contains the volume of many p'ras measures, he never ate a k'zayis of forbidden food within the time span of k'dei achilas p'ras. To be liable, the loaf or sandwich being eaten must have at least a k'zayis of forbidden food for every p'ras measure of bread.
The second part of the Mishnah:
The second part of the Mishnah deals with a completely new topic: Incidental to the time measure of "k'dei achilas p'ras", the Mishnah lists other halachos where this measure applies. This is not an exhaustive list, but rather two matters involving eating or drinking that must be done within the time of k'dei achilas p'ras.
A. Eating tamei food:
This matter relates to a rabbinic law, one of the eighteen strictures decreed - as we remember from Tractate Shabbos - at that gathering where the students of Beis Shammai outnumbered the students of Beis Hillel, when they convened in the attic of Chananyah ben Teradyon. One of the laws they enacted is that a person who eats a meal, or even a casual snack, of tamei food becomes tamei himself. Under Torah law, a Jewish person only becomes tamei from an av hatumah, a primary source of tumah like a sheretz, a zav, a metzora, or a person who became tamei from a corpse, and not from food. It is impossible for food or drink to be an av hatumah, and therefore on a Torah level, food and drink do not make a person tamei.
The concern of the Sages was that a person might eat a meal combining tamei food and pure Terumah, and inside his mouth, the Terumah would come into contact with the tamei food. Terumah does indeed become tamei from tamei food under Torah law, and he would end up invalidating and defiling the Terumah in violation of a Torah prohibition. Therefore, the Sages sought to separate a meal or casual eating of tamei food from the eating of Terumah, and they established that once a person eats a meal or casual snack, he must immerse in a mikvah before eating Terumah. Even though eating Terumah is an act done only by a kohen, since only a kohen eats Terumah, and this is the main concern here, the Sages established a blanket rule that anyone who eats tamei food, and at least a casual eating, becomes tamei as a sheni letumah which invalidates Terumah, and he cannot eat or drink Terumah until he immerses in a mikvah.
And how much must one eat for it to be considered a meal or casual eating? Regarding food, this is half a p'ras. Since a p'ras is half a loaf, this means a quarter of a loaf: According to Rashi, who holds that a whole loaf is eight egg volumes and a p'ras is four, half a p'ras is the volume of two eggs; and according to the Rambam, who holds that a loaf is six egg volumes and a p'ras is three, half a p'ras is the volume of one and a half eggs. A person who ate tamei food in the volume of one and a half eggs or two eggs becomes tamei as a sheni, and he must immerse in a mikvah before eating Terumah. And in what time span must he eat this half p'ras? Within k'dei achilas p'ras, those same three or four minutes.
B. A kohen who drank wine and served in the Temple:
The second topic is the prohibition against a kohen drinking wine or other intoxicating beverages and subsequently performing the Temple service. The verse forbids this: "Yayin v'sheichar al teisht" - do not drink wine and intoxicating liquor, and the punishment for this is death by Heaven - a kohen who performs the service while under the influence of wine. And what is the definition of "under the influence"? That he drank at least a revi'is of wine, and in what time span? Within k'dei achilas p'ras, the exact same concept.
And these are the words of the Mishnah: "Achal ochel tamei, v'shasah mashkeh tamei, shasah revi'is yayin v'nichnas lamikdash - im shaha k'dei achilas p'ras" - he ate tamei food, and drank tamei liquid, drank a revi'is of wine and entered the Temple - if he delayed the time of k'dei achilas p'ras. Meaning, he ate tamei food in the volume of at least half a p'ras, or drank tamei liquid in the volume of at least a revi'is, or drank a revi'is of wine and entered the Temple - if the duration of time in which he consumed that half p'ras of food, or drank that revi'is of tamei liquid, or that revi'is of wine that intoxicates the kohen, was within k'dei achilas p'ras, the liabilities take effect. The Mishnah does not elaborate on what happened afterward, and this is its main point here.
The Opinion of Rabbi Eliezer:
Regarding the last matter, drinking wine and the prohibition to perform the service, Rabbi Eliezer says: "Im hifsik bah o shenatan letocho mayim kolshehu" - if he paused during it or put any amount of water into it, he is exempt. A person who paused in the middle of drinking, and drank exactly one revi'is and not a drop more, but did not drink it in a single gulp, but rather drank half, waited a little, and drank the second half - since the drinking was spread out a bit, this is not considered the intoxication that prohibits him from the service in the Beis Hamikdash. The same applies if he put a little water in the wine to dilute it: even if he now drank exactly a full revi'is in a single gulp, he is exempt from death at the hands of Heaven. Rabbi Eliezer concedes that if he drank more than a revi'is, neither a slight pause nor putting water in the wine is effective.
The Halachah:
The halachah is in accordance with Rabbi Eliezer: a person who drank the wine in two gulps and drank exactly one revi'is, may perform the service; whereas one who drank more than a revi'is, even with a pause in the middle, may not perform the service as long as he feels the effects of the wine. While the service of the Beis Hamikdash is not practically applicable nowadays, there is a practical halachah here: a kohen who drank a revi'is of wine does not go up to the duchan to recite the Priestly Blessing, and a halachic authority who drank a revi'is of wine cannot render halachic rulings as long as he is under the influence of the wine.