Bikkurim, Chapter Two, Mishnah 11 - the final mishnah of the chapter, which closes the discussion of the koy. In this chapter we learned in which ways the koy resembles a domesticated animal and in which ways it resembles a wild animal. Now the mishnah asks: "Keitzad eino shaveh lo lechayah velo livheimah" - in which matters is it unlike a wild animal, an undomesticated creature, and also unlike a domesticated animal?
The ways in which the koy is like neither a wild animal nor a domesticated animal:
"Assur mishum kilayim im hachayah ve'im habeheimah" - the prohibition of kilayim includes the ban on working two different species of animals together, as well as the ban on mating them with one another. The koy is not considered a species that may be paired either with a wild animal or with a domesticated animal. The Tiferes Yisrael raises a difficulty here: after all, in general one does not mate one species with another species, whether both are domesticated animals or both are wild animals, so what is novel about the koy? This question is not easily resolved, but in any event the mishnah maintains that in this respect the koy is neither like a wild animal nor like a domesticated animal.
"Hakotev chayaso uveheimto livno, lo kasav lo es hakoy" - if a person deeded to his son as a gift all the wild animals in his possession and all his domesticated animals, the koy is not included in that gift. The koy is not deeded to him the way a wild animal and a domesticated animal are, since it is a separate species in its own right.
"Im amar hareini nazir shezeh chayah o beheimah, harei hu nazir" - one who says "I am hereby a nazir" and makes his vow contingent on the koy being a wild animal, or on its being a domesticated animal, in either case the nezirus takes effect upon him.
It is worth noting precisely that the last item, the laws of nezirus, is not really counted among the ways in which the koy resembles neither a wild animal nor a domesticated animal. For in any formulation a person might use he will be a nazir: whether he said it is a wild animal, whether he said it is a domesticated animal, whether he said it is both a wild animal and a domesticated animal, and whether he said it is neither a wild animal nor a domesticated animal - in all of these the nezirus takes effect. The reason is that each of these statements contains an element of truth, and since part of each one is correct, we rule stringently. As long as his words are correct even partially - that the koy partially resembles a wild animal and a domesticated animal, or that it resembles neither a wild animal nor a domesticated animal - the nezirus takes effect upon him. Therefore this is not truly counted as one of the matters in which the koy is neither like a wild animal nor like a domesticated animal.
In the remaining matters the koy is like a wild animal and a domesticated animal alike:
Shechitah: the koy requires shechitah, exactly as a wild animal is slaughtered and a domesticated animal is slaughtered.
Tumah of a neveilah: if it died without shechitah, the tumah of a neveilah applies to it, a law that applies both to a wild animal and to a domesticated animal, and so too with the koy.
A limb severed from it: a limb severed from the koy carries tumah just as is the case with a wild animal and a domesticated animal - that limb takes on the status of a neveilah even though the rest of the animal is alive and well. With the koy the law is the same.
In summary: in this mishnah we learned the ways in which the koy is like neither a wild animal nor a domesticated animal - the prohibition of kilayim with both of them, and its exclusion when one deeds his wild animals and domesticated animals to his son; and we clarified that the law of nezirus is not counted among these ways, since with any statement the nezirus takes effect on account of stringency. In the remaining matters, by contrast - shechitah, the tumah of a neveilah, and the tumah of a severed limb - the koy is like a wild animal and a domesticated animal alike.