Matthew Poole and continuators on Exodus 13:13

13 And every firstling of an ass thou shalt redeem with a lamb: and if thou wilt not redeem it, then thou shalt break his neck , and all the first-born of man amongst thy children shalt thou redeem.

An unclean creature, and therefore this rule was to be observed in all other unclean creatures, as appears, 1. because the reason of this law is common to all such. 2. by comparing this place with Numb. 18. 15. 3. because the first-born of all beasts were appropriated to God, and because many of them were unclean and so could not be sacrificed, there was no other way of offering them to God but by redemption or a price paid for them. And the single exception of the price of a dog in this case, Deut. 23. 18. doth sufficiently intimate, that the price of all other unclean creatures was allowed and required. The ass alone is here named for all the rest, because this creature was most common and most useful, and yet was not to be spared: whence it was easie to infer, that this course was much rather to be observed in other creatures which were of less use.

Or, cut off his neck or head, as the word is used Deut. 21. 4. Isa. 66. 3. because being consecrated to God it was not to be applyed to any profane or common use.

Marginal references: Or, kid.