Avodah Zarah 073

12:
We continue now our study of the meaning of the terms used in our present mishnah. It is important to recall the basic teaching of this mishnah: it is forbidden to derive any benefit whatsoever from any of the items listed in our mishnah, and should one of them become mixed up with other permitted items it makes all of them forbidden.

13:
We come now to the item called 'a donkey's redemption'. In biblical times a firstborn was considered to possess some kind of inherent sanctity. It was an act of piety to offer "that which opens the womb" back to God. (There is some evidence that in Canaanite society – and its offshoot, Carthaginian society – even firstborn male children were "passed through the fire" to their god. We discussed this at length ten years ago when we studied Sanhedrin 097.)

14:
The Torah [Exodus 34:19-20] commands as follows:

The basic idea is that the firstborn male of an animal that could be offered ("cattle or sheep") was to be sacrificed on the altar in the Bet Mikdash. Donkeys, like human beings, could not be sacrificed on the altar. Therefore donkeys, like human beings, must be redeemed.

15:
The ruling is that a firstborn male donkey must be redeemed. The ceremony is similar to the parallel ceremony, pidyon ha-ben, in which a human child is redeemed. The owner of the donkey must offer to the kohen (priest) of his choice a sheep or goat as the redemption price of his animal. It is also possible to redeem the donkey with money: the only difference is that redemption money must equal the value of the animal whereas a sheep or goat suffice regardless of their value.

16:
You can watch a ceremony of A Donkey's Redemption that took place in 2007 in Moshav Elyashiv in Israel. In this case the goat now belongs to the kohen and he can do with it whatever he pleases – probably he will just add it to his flock or sell it at a profit. The redeemed donkey is now like any other donkey.

17:
However, our mishnah is not referring to a redeemed donkey but to one that is not redeemed or has not yet been redeemed. It is forbidden to derive any benefit from such an animal until it has been redeemed. Should an unredeemed firstborn donkey become mixed up with other donkeys they are all now forbidden.

18:
The next item in our mishnah's list is 'meat and milk'. It would be very tempting to simply explain what almost every Jew already knows: it is forbidden to derive any benefit from an admixture of meat with any dairy product. But this is not the meaning of our mishnah.

19:
Three times, rather enigmatically, the Torah stipulates:

The Gemara [Ḥullin 115b] explains:

And not just a kid in its own mother's milk but any meat in any milk or dairy produce.

It is well known that in matters of kashrut when something forbidden gets mixed up with something permitted it does not render the whole forbidden if the prohibited element is less than one sixtieth (1.67%) of the whole admixture. (Thus a tiny drop of milk that somehow gets into a large pan of chicken soup will not render the soup prohibited if the amount of milk can be assessed as being less than one sixtieth of the whole.)

20:
Since our mishnah refers to what is rendered prohibited "with any amount" it cannot be referring to an ordinary admixture of milk and meat. The commentators note that all the other items are countable: one item getting mixed up with other similar items, except that they are not distinguishable. Therefore, the meaning of this item in our present mishnah is as follows:

When a piece of meat became prohibited by contact with some dairy product and it then becomes mixed up with others pieces of meat they are all rendered prohibited.

21:
The last item in the list of our mishnah is simple to explain: only sacrifices could be offered in the priests' court of the Bet Mikdash. If some priest slaughtered his own animal for his personal use using the amenities of the Bet Mikdash the slaughtered animal is prohibited and should the carcass become mixed up with other permitted non-sacrificial carcasses they are all prohibited. The distinction between sacral meat and secular meat derives from the verse in the Torah which permits secular meat:

This "your settlements" is the right place to slaughter secular meat and "the place where God chooses to establish His name" is the right place to slaughter sacral meat.