Before us is mishnah 5, the last in chapter 6. In the previous mishnah we dealt with the offspring of an animal bought with the price of a dog, an animal given as the hire of a harlot, and the harlot herself, and now the mishnah returns to discuss the offspring of the other categories of animals disqualified for the altar that were listed in the first mishnah of the chapter. And so we learned: "Kol ha'asur legabei mizbe'ach - v'ladan mutarim" - all of that list of animals forbidden to be brought upon the altar, their offspring is permitted as an offering.
The principle: "Zeh v'zeh gorem mutar":
This halachah rests on the rule of "zeh v'zeh gorem mutar" - when two factors act together to produce a single result, and only one of them is forbidden, the result is permitted. In our case: if a forbidden animal, for example an animal that was worshipped as idolatry, then became pregnant from a male that is a permitted animal, the offspring is a combination of the forbidden mother and the permitted father, and for that reason it is permitted to be brought upon the altar. The reverse follows as well: had the forbidden animal - one that was worshipped, for example - become pregnant from an animal that was itself worshipped, so that both factors are forbidden, the offspring would be forbidden.
An animal that was already pregnant when it became forbidden:
Everything said above is based on the assumption that the animal first became forbidden and only afterward became pregnant. But regarding an animal that was already pregnant at the time it became forbidden, the rule is that the offspring growing in its mother's womb is like its mother's thigh, like any other of the animal's limbs. Just as one who designates an animal for idolatry renders all of it forbidden with all its parts - its legs, its heart, its lungs and its liver - so too the fetus growing inside it is forbidden, since it was part of what was designated for idolatry. This halachah applies to those animals to which the matter is relevant, such as an animal that was the object of bestiality, one set aside for idolatry, and one that was worshipped, and it does not apply to cases such as an animal that committed bestiality, since that is a male.
The offspring of a tereifah - a dispute:
From here the mishnah moves to a more complex matter - the tereifah. A tereifah is an animal that sustained a fatal injury that will not allow it to go on living. What is the law if a pregnant mother became a tereifah, and thereby became forbidden as an offering, but before its death it gave birth to a completely healthy offspring? It is difficult to say that the offspring has its mother's status, since it emerges healthy and whole. On this the Tanna'im disagreed:
Rabbi Eliezer says: "Lo yikrav al gav mizbe'ach" - the offspring's law is like every other case of "it is like its mother's thigh." Its halachic status is one of prohibition by virtue of its having been part of the mother, and the fact that in practice it did not die makes no difference at all - the halachic status of a tereifah still applies to it.
And the Sages say: "Yikrav" - there is a difference between a tereifah and the other disqualifications. The other disqualifications are based on halachic and legal definitions, whereas the matter of a tereifah is a physical reality in the animal's body. The offspring born from the tereifah mother is not a tereifah at all, and therefore it is not disqualified.
From here on the mishnah raises two additional matters, which have no real connection to temurah or to the subject of animals disqualified for the altar, but are drawn in here because of the discussion of the offspring of a tereifah.
1. A kosher animal that nursed from a tereifah:
Rabbi Chanina ben Antigonus says: a kosher animal that nursed from a tereifah - such as a calf or a lamb nursing from a mother that is a tereifah - if during the last twenty-four hours the young animal was sustained by this milk alone, it turns out that the living animal is being maintained by the strength of a disqualified animal. It is the milk of a tereifah, and for that reason the young animal too is disqualified. During those twenty-four hours after the nursing it may not be brought upon the altar as an offering. The halachah does not follow this opinion.
2. Consecrated animals that became a tereifah:
An animal that was consecrated as a korban and then became a tereifah - we do not redeem it in order to buy a new animal with the money. To understand this, we must clarify the difference between a tereifah and a blemished animal:
An animal that lost its leg below the knee: This is not a tereifah but a blemished animal, and it cannot be offered. In such a case it has a permanent blemish, and it should be redeemed, with the money used to buy a replacement korban. A trace of sanctity remains in the redeemed animal, and therefore, although it is no longer a korban, it may only be slaughtered and eaten; one may not work with it, shear it, or drink its milk.
An animal that lost its leg above the knee: This is not merely a blemished animal but a tereifah. If it were redeemed, he would indeed have money to buy a new korban, but what would he do with the redeemed animal? The only thing permitted with it is eating, and eating it is forbidden, since it is a tereifah. In the end he would feed it to his dogs, and that is a complete disgrace to what had been a korban designated to be brought upon the altar of Hashem. Therefore it is left to graze until it dies, and it is not redeemed.
This is what the Mishnah says: "Kol hakodashim shena'asu tereifah - ein podin osam, she'ein podin es hakodashim leha'achil lakelavim" - all consecrated animals that became a tereifah are not redeemed, for we do not redeem consecrated animals in order to feed them to dogs. Consecrated animals are not redeemed, even when they have a permanent blemish, when their only purpose after redemption would be food for dogs. This is the halachah.