Bikkurim, Chapter 2, Mishnah 9. As we mentioned in the previous Mishnah, our Mishnah comes to spell out one side of what the previous Mishnah stated: "Keitzad shaveh l'chayah" - in what way is it like a wild animal? The koy is a creature whose identity was never settled: is it a chayah, that is, a wild animal, or is it a domesticated animal? In what respects, then, does the koy share the laws of a wild animal?
"Damo ta'un kisui k'dam chayah":
A wild animal, like a bird, requires covering of the blood after slaughter, whereas a domesticated animal - such as a cow or a sheep - does not require its blood to be covered. One who slaughters a deer must cover its blood, exactly as one covers the blood of a chicken. The Mishnah therefore rules: "Damo ta'un kisui k'dam chayah" - its blood requires covering like the blood of a wild animal. Since its nature is unknown, we must be stringent and treat it as though it may be a wild animal, and cover its blood.
The Mishnah now mentions two laws that do not stem from its resemblance to a wild animal, but rather from caution in the opposite direction:
"V'ein shochtin oso b'Yom Tov" - we do not slaughter a koy on Yom Tov, because of the problem of covering its blood.
"V'im sh'chato, ein mechasin es damo" - and if one did slaughter it, we do not cover its blood on Yom Tov.
The reason for this, according to some opinions: onlookers will assume that if its blood is covered on Yom Tov, it must certainly be a wild animal. And why does that matter? There is a further law that certain fats called cheilev are forbidden to eat in a domesticated animal and permitted in a wild animal. Since the fat of a wild animal is permitted, we are concerned that people will conclude that the koy is definitely a wild animal, and will come to eat its fat. For this reason we do not cover its blood on Yom Tov, and consequently we do not slaughter it at all. In any case, these two laws do not stem from its resembling a wild animal, but from taking into account the possibility that it is not a wild animal.
"Chelbo metamei b'tumas neveilah":
Here we find an unusual twist, and this is the difference between a domesticated animal and a wild animal:
In a domesticated animal: its fat is forbidden to eat and is not considered like its flesh. Therefore, an animal that died and became a neveilah - its flesh conveys the tumah of a neveilah, but its fat does not.
In a wild animal: its fat is permitted to eat and is considered exactly like its flesh. Therefore, if it died and was not slaughtered, the law of neveilah tumah applies to its fat as well.
It emerges that neveilah tumah follows the question of whether the part is considered flesh that is permitted to eat or not. For this reason, when we come to be stringent and treat the koy as a wild animal, we impose tumah on its fat as well: "Chelbo metamei b'tumas neveilah" - its fat conveys the tumah of a neveilah, like the law of a wild animal.
The Mishnah qualifies this, however: this tumah is only a doubt. Therefore, a person who entered the Temple after possibly having become tamei from that fat does not bring a korban on the basis of this tumah, since he never knew with certainty that he had become tamei, and there is nothing here but a doubt.
"V'ein podin bo peter chamor":
The redemption of a firstborn donkey must be done with a seh, that is, with a lamb. Even though there is a possibility that the koy is of the category of a seh - and particularly according to the opinion that it comes from a male goat and a female deer, so that perhaps the goat side predominates and it belongs to the family of the flock - we must be stringent and say that perhaps it is not considered a seh but a wild animal. And this is the side with which the Mishnah opened, "Keitzad shaveh l'chayah": the possibility that it is a wild animal, from the side of the deer. Therefore we do not redeem a firstborn donkey with it.
In summary: in this Mishnah we learned the details in which the koy is equivalent to a wild animal: its blood requires covering like the blood of a wild animal, and its fat conveys the tumah of a neveilah - except that this tumah is a doubt and one does not bring a korban for it, and one does not redeem a firstborn donkey with it, lest it not be a seh. We also noted the two laws that stem specifically from the opposite concern: that we do not slaughter it on Yom Tov, and if one did slaughter it, we do not cover its blood, lest people come to establish it as a definite wild animal and permit its fat to be eaten.