Peah Chapter 4, Mishnah 10. This mishnah comes to define the obligation of leket. As we have learned, leket is what falls during the process of harvesting, and that is exactly the definition the mishnah sets before us.
"Eizehu leket? Hanosher bish'as ketzirah" - anything that falls to the ground during the harvesting and is not gathered together with the rest of the grain belongs to the poor person.
Falling because of an accident:
The mishnah continues: "Hayah kotzer, katzar melo yado... venafal miyado la'aretz - harei hu shel ba'al habayis". The harvester cut an armful, and in the language of the mishnah "yad" means the arm, as the Rambam defines it, and not the palm of the hand, since the next case in the mishnah is "melo kumtzo" - what fills his palm. Whether he cut an armful or a fistful, he encircles the bundle of grain with his arm or with his palm, and in the middle of doing so a thorn struck him and everything he had cut fell to the ground.
Why is this not considered leket? Two reasons are given:
Because it is an accident: this is not something that happened in the normal course of the harvesting, but rather because of an outside event - the thorn that wounded him and caused him to drop the grain. Therefore the grain belongs to the owner of the field.
Because of the timing: some explain that by the time it fell he had already cut it, and the falling happened afterwards. For this reason it is not "hanosher bish'as ketzirah" - during the harvesting itself - but something that occurred after it, and it belongs not to the poor person but to the owner.
"Toch hayad v'toch hamagal":
The mishnah continues: "Toch hayad v'toch hamagal - la'aniyim". If it fell from within the hand or from within the magal, that is, the sickle, the tool with which he harvests, then what falls belongs to the poor. "Achar hayad v'achar hamagal" - if it fell outside the hand or the arm and outside the sickle, it belongs to the owner, since this is not considered part of the harvesting but rather something external and secondary to it.
What exactly is meant by "toch hayad v'toch hamagal"? There are three ways to learn the mishnah:
Both conditions together: it must be both within the hand and within the sickle for the poor person to acquire it. According to this, "achar hayad v'achar hamagal" means that one of the two is enough - either beyond the hand or beyond the sickle.
One of them is enough: "toch hayad v'toch hamagal" means this one or that one, and the fulfillment of one of the two conditions suffices. According to this, "achar hayad v'achar hamagal" requires both conditions together: neither within the hand nor within the sickle, and only then does it belong to the owner.
Two separate scenarios: "yad" and "magal" are two entirely different types of cases. "Toch hayad" refers to one who harvests by pulling with his hand, without a tool: if it fell from within the hand, it goes to the poor, and if it fell outside the hand or the arm, it goes to the owner. "Toch hamagal" refers to one who harvests with a tool, and these are two separate matters.
The tip of the hand and the tip of the sickle:
What is the law when it fell exactly at the edge - at the tip of the bundle in his hand or at the tip of the sickle? On this the Tannaim disagree:
Rabbi Yishmael says: it goes to the poor - we view it as though it were within the hand or within the sickle, out of consideration for the poor person.
Rabbi Akiva says: it goes to the owner - we view it as though it were outside the hand and outside the sickle, and therefore it belongs to the owner of the field.
In summary: in this mishnah we learned the definition of leket - "hanosher bish'as ketzirah"; that a fall caused by a thorn is not leket, both because it is an accident and because it happened after the harvesting; the rule of "toch hayad v'toch hamagal" with its three ways of being understood; and the dispute between Rabbi Yishmael and Rabbi Akiva regarding what falls at the tip of the hand and at the tip of the sickle.