Orlah 2:11-12

Orlah 2:11

If regular leaven and terumah leaven both fell into dough and neither one was sufficient to leaven the dough by itself but combined they are, Rabbi Eliezer says the status of the dough follows whichever leaven fell in last. The Sages say that it makes no difference whether the prohibited leaven fell in first or last – it doesn’t render the dough prohibited unless it’s sufficient to leaven it.

Orlah 2:12

Yoezer of Bira was one of the students of Beis Shammai. He reported that he asked Rabban Gamliel the Elder about the case of the two leavens (as in 2:11) and he replied that it doesn’t render the dough prohibited unless it’s sufficient to leaven it.