[If] one takes sourdough from a dough whose challah has not been separated and places [it] into a dough whose challah has been separated, if he has a supply from elsewhere, he may separate [challah] proportionally; but if not, he must take one challah for the whole [dough].

Similarly, harvested olives that were mixed with gleaned olives, [or] harvested grapes [that were mixed] with oleilos grapes, if one has a supply from elsewhere, he may separate [tithes] proportionally. But if not, he must separate terumah and terumas maaser for the entire [mixture], and the remaining maaser rishon and maaser sheni proportionally.

[If] one takes sourdough from a wheat dough and places [it] into a rice dough, if it has the taste of grain, it is obligated in challah; but if not, it is exempt. If so, regarding what did they say [that] tevel forbids [a mixture even] in minute concentration? A kind with its [like] kind; but with an unlike kind, [tevel prohibits only] when [it] imparts taste [to the mixture].

[If] two women made two kav [doughs], and they touched one another, even if they are of the same kind, they are exempt. But when they belong to one woman, a kind with its own kind is obligated, but with a different kind it is not obligated.