Mishnayos Peah Perek 1 Mishnah 3

מתחלת השדה ומאמצעה – And one does not need to place down the “corner” at the end of the field, as it is written (Leviticus 19:9): “[When you reap the harvest of your land,] you shall not reap all the way to the edges of your field…” said the Torah: Give the “corner” and even though you still have standing grain to reap.

ובלבד שיתן בסוף כשיעור – Even though the Bible extends [the application (of the word פאה ) to include] the beginning and in the middle of the field which have [upon them] the Torah-obligation of [giving] Peah [upon it] to what he had given, nevertheless, he is only exempt if he gives at the end of the field a payment [equivalent to] the measurement of one-sixtieth, together with what he had given in the middle and at the beginning, such is derived in the Jerusalem Talmud. And Maimonides explained that only as long as he gives at the end according to the measure of PEAH that is required for the entire field, that he must set aside at the end of the field one-sixtieth apart from what he had left at the beginning and middle [of the field].

ואם שייר קלח אחד – At the edge of the field and left it for the [obligatory] “corner”, he relies upon it, and everything that he left in the middle and at the beginning, the law of “Peah” is upon it.

ואם לאו – If he did not leave even one stalk at the edge of the field for [the fulfillment of the commandment of] “the corner,” what he had left in the middle and at the beginning [of the field] are not considered “the corner” but it has only the principle of HEFKER/renunciation of ownership and he (Rabbi Yehuda) disagrees with [the opinion of] Rabbi Shimon who says, that nevertheless, it is considered “PEAH/the corner” - but that the owner of the field is not exempted [from his obligation to give PEAH] with this [alone]. And the Halakha is according to Rabbi Shimon.