Levítico 19:9 Halajá: Mishneh Torah, Gifts to the Poor, Shulchan Shel Arba, Mishneh Torah, Foreign Worship and Customs & Mishneh Torah, Positive Mitzvot

And so it is with leket [overlooked gleanings] as one reaps and binds, one may not gather the fallen stalks at the time of reaping, but rather one should leave them for the poor, as it is said, (Lev. 23:22) Or gather the gleanings of your harvest. If one transgresses [the negative mitzvah against reaping one's field completely] and reaped them and even kneaded and baked them, one should give them to the poor, as it is said, (Lev. 23:22) You shall leave them for the poor and the stranger. If it is destroyed or burned after one has gleaned but before one has given to the poor, one deserves punishment.

All of these gifts for the poor as they are in the Torah only apply to the Land of Israel, like gift offerings and tithes. Thus Scripture says, (Lev. 19:9, 23:22) When you reap the harvest of your land, [and] (Deut. 24:19) When you reap the harvest in your field. [But] it has already been explained in the Talmud¹⁴See Babylonian Talmud Chullin 137b. that the category of péah applies outside of the Land of Israel from rabbinic law, and it appears to me that it makes sense for the remaining types of gifts for the poor to all apply to outside of the Land of Israel from rabbinic law as well.¹⁵See Mishnah Kiddushin 1:9. In this law as well as the next, Maimonides makes a distinction between laws that are from the Torah itself and rabbinic rulings. While laws from the Torah are more directly authoritative, the laws of the rabbis rest on the authority of a tradition of sacred interpretation and were considered just as binding as the laws of the Torah. Indeed, some rabbinic laws carried very severe punishments for their transgression to discourage challenging their authority. The rabbinic law seeks to clarify the intent of the Torah, filling in the gaps that the Torah does not make clear. In this instance, the location of where these laws are in force in the Jewish community and the minimum amount that needed to be given are details lacking in the Torah that the rabbis fill in.

Anything (1) that people eat, (2) that is raised from the soil, (3) that is supervised, (4) that is gleaned all together at once, and (5) that is put into storage is subject to the giving of the péah portion, as it is said, (Lev. 19:9, 23:22) When you reap the harvest of your land.¹⁷See Mishnah Péah 1:4 as a source for this definition.