Temurah 1:3-4

Temurah 1:3

The laws of temurah do not apply to exchanging limbs for fetuses or vice versa, nor to exchanging limbs or fetuses for whole animals or vice versa. Rabbi Yosi says that temurah does apply to exchanging limbs for whole animals but not vice versa. This, he says, is because if a person declares, “Let this animal’s leg be a burnt offering,” the entire animal becomes a burnt offering. Similarly, if a person says, “This animal’s leg instead of that animal,” then all of the animal should become temurah.

Temurah 1:4

Medumah (a mixture of trumah and secular produce) only renders other produce medumah proportionate to the trumah in the mixture. Secular dough leavened with trumah only prohibits other dough proportionate to the trumah leaven in it. Drawn water disqualifies a mikvah only proportionately.