3,641. A Dough Jointly Owned by a Jew and a Non-Jew Who Converts
Hilchos Bikkurim 7:9
(In the previous halacha, we discussed two non-Jews who made a dough large enough to require taking challah and then divided it into smaller portions.) If two Jews make a dough in this manner and then divide it, after which each adds to his share of the dough until it’s large enough to require challah, then challah need not be taken. This is because there was a time when they would have had to take challah from the original dough, but it was exempt from challah because the dough was made to be divided between them.
Hilchos Bikkurim 7:10
But what if the dough was jointly owned by a non-Jew and a Jew, and they divided it? If the non-Jew subsequently converts and then adds to his part of the dough, and the Jew adds to his part of the dough, so that each part reaches the volume that requires challah to be taken, then challah must be taken from the dough of the Jew, but it need not be taken from the dough of the convert. [In this case, the dough wasn’t made to be divided. Since the non-Jew is joint owner of the whole, challah doesn’t apply to it, with the result that the Jew’s share of the dough was never large enough to require challah to be taken.]