Some people make sure not to eat Hames which was sold on Mosa’eh Hag until they are sure the rabbi has already bought it back from the non-Jew. Nevertheless, the Poskim say that technically, one can eat it immediately, since the non-Jew does not mind if the Jew eats the Hames, as he will deduct it from the sum that he owes for the purchase. Especially today, most contracts for selling Hames have a clause which states explicitly that the Jew may benefit from the Hames immediately after Pesah. Hacham Bension wrote that this is the proper way to formulate the agreement, and if it was not written, he should wait. However, there is room to rely on the lenient position and benefit immediately.
In Eres Yisrael, one should wait until 72 minutes after sunset (after the Hag.). Outside of Israel, one does not have to wait that long, since anyway, the second day of Hag in the diaspora is M’drabanan.
SUMMARY
One may eat Hames sold to a non-Jew immediately after the conclusion of Hag and not wait for the rabbi to buy it back.
