פירוש על פאה 4:6

נכרי שקצר את שדהו וכו' – as it is written concerning gleaning and the corner of the field (Leviticus 19:9): “When you reap [the harvest of your land…],” excluding that when heathens reaped it, and concerning that which is forgotten, it is written (Deuteronomy 24:19): “When you reap the harvest in your field and overlook a sheaf in the field, [do not turn back to get it]..,” from here they said that a heathen which reaped his field and afterwards converted is exempt.

Introduction This mishnah deals with a non-Jew who harvests his field and then converts. Non-Jews are not liable for the laws of peah, but Jews are, so the question is does he have to give the peah after he has already harvested the whole field.

שאין השכחה אלא בשעת עמור – and at the time of carrying sheaves home, he was a convert and liable in all the commandments, but the Rabbis hold that since there is the forgotten sheaf of the Omer, and there is that which is forgotten with the standing corn, as it is written (Deuteronomy 24:19): “and overlook a sheaf in the field,” to include that which is forgotten with the standing corn, that which exists with that which is forgotten of the standing corn exists with that which is forgotten of the grain sheaf, and that convert who harvests while reaped that which was not that which was forgotten of the standing corn for at that time he was a heathen, and even though he has not converted, it is not that which is forgotten of the grain sheaf. But the Halakha is not according to Rabbi Yehuda.

A non-Jew who harvested his field and then converted, he is exempt from [leaving] gleanings, the forgotten sheaf and peah. The new convert is exempt from giving all of these agricultural offerings for a field that he harvested before he converted because according to the opinion in this section, the obligation to give these offerings is set at the time of the harvest. Since he was not obligated when he harvested them, because he was not Jewish, he does not become obligated after he converts.

Rabbi Judah makes him liable to leave the forgotten sheaf, since he becomes liable for the forgotten sheaf at the time of their binding. Rabbi Judah says that the obligation to give forgotten sheaves is only set at the time at which the sheaves are bound together. Therefore, if he converts before he binds the sheaves, he is obligated to give the ones that are forgotten. We shall learn more about these laws later in this tractate.