[If] one consecrated standing grain and redeemed standing grain, he is liable. [If he consecrated] sheaves and redeemed sheaves, he is liable. [If he consecrated] standing grain and redeemed sheaves, it is exempt, since at the time of its [potential] liability it was exempt.

[If] a non-Jew reaped his field and then became a proselyte, he is exempt from the [obligations of] leket, shich'chah, and peah.  R' Yehudah obligates [him] in the law of shich'chah because the law of shich'chah takes effect only at the time that the sheaves are removed [to the main pile].