Peah 1:2-3

Peah 1:2

One does not leave less than one-sixtieth of his field as peah. Even though the Torah gave no prescribed measurement for peah, the Sages set one based upon the size of one’s field, the number of needy people and the yield of the crop.

Peah 1:3

Peah can be given from the place where they start to reap at the beginning of the field and from its middle. Rabbi Shimon says this only counts as peah when he gives the required minimum from the end of the field. Rabbi Yehuda says if he left even one stalk at the end of the field, it combines with what he took from elsewhere to serve as peah. If he doesn’t do this, the rest of what he left doesn’t count as peah but as hefker (property he declared ownerless).