Sefer HaChinuch ספר החינוך

To leave the gleanings in the field: To leave the gleanings to the poor — and that is what falls from the sickle at the time of the harvesting, or from the hand at the time of the plucking, as it is stated with the gleanings (Leviticus 19:10), “to the poor and to the stranger shall you leave them.”

I have written what I have known from the roots of the commandment on the commandment of the corner (Sefer HaChinukh 216).

From the laws of the commandment is that which they, may their memory be blessed, said (Mishnah Peah 6:5), “One or two sheaves are gleanings, three are not gleanings” — meaning to say, if three sheaves or more fall together from the hand of the harvester, the three of them [go] to the owner of the field; as the law of gleanings is only with a little, and specifically when the gleanings fell from the harvester without duress (Mishnah Peah 4:10). But if a thorn struck his hand and they fell, this is not gleanings. And [if there] is a doubt [whether they are] gleanings, they are [considered] gleanings; as it is stated (Psalms 82:3), “the poor and destitute shall you justify” — justify from what is yours and give [it] to him. And the law of produce that is found in ant holes (Mishnah Peah 4:10); the law of a sheave of gleanings that is mixed up in a pile (Mishnah Peah 4:2); and the rest of its details are elucidated in Tractate Peah. And with regards to in which place it is practiced and who is obligated about it and the punishment of one who transgresses it, it is all like the corner.