And in what [case] did they say: “Any [agent] that leavens, spices, or generates a prohibited mixture of chullin and terumah is to be treated with stringency”? A type in a like type. To be treated [sometimes] leniently and [sometimes] stringently? A type in an unlike type. How so? Sourdough of wheat that fell into a dough of wheat, and there is enough of it to leaven, whether there is enough to nullify in one hundred and one and whether there is not enough to nullify in one hundred and one, it is forbidden. [If] there is not enough to nullify in one hundred and one, whether there is enough of it to leaven or whether there is not enough of it to leaven, it is forbidden.

“To be treated [sometimes] leniently and [sometimes] stringently? A type in an unlike type.” How so? For example, where pounded [beans] were cooked with lentils, and they had the capacity to impart flavor, whether they were capable of being nullified in one hundred and one, or whether they were not capable of being nullified in one hundred and one, it is prohibited. If they did not have the capacity to impart flavor, whether they were capable of being nullified in one hundred and one, or whether they were not capable of being nullified in one hundred and one, it is permitted.

Sourdough of chullin that fell into a dough, and it is capable of leavening [the dough], and afterwards sourdough of terumah or sourdough of kilei hakerem fell in, and it is capable of leavening, it is prohibited.

Sourdough of chullin that fell into a dough and leavened it, and afterwards there fell in sourdough of terumah or sourdough of kilei hakerem, and it is capable of leavening [the dough], it is forbidden. R' Shimon permits.