John Calvin on Exodus 34:19-27

19. All that openeth the matrix is mine. He here defines what the offering was to be, viz., that they should redeem their children as well as the unclean animals at a price; but that they should bring into the tabernacle whatsoever could be offered in sacrifice. But God would not have their own sons consecrated to Him, because He had chosen the tribe of Levi, as we shall see elsewhere; they were therefore to remain free and in their own power after a pecuniary compensation. In the same way, unclean animals might be applied to domestic purposes, viz., after God’s price had been paid, since to Him they belonged, and He claimed them for Himself. But if any should not put so high a value on an ass or other unclean animal, the Law commanded that its neck should be broken; for otherwise it would have been sacrilege to reap profit from God’s property, or, what is the same, to transfer to their private use what God had adjudged to Himself.

Leviticus 27

Leviticus 27:26

26. Only the firstling of the beasts, which should be the Lord’s firstling, no man shall sanctify it: whether it be ox or sheep, it is the Lord’s.

26. Veruntamen primogeniture quod jure primogeniturae debetur Jehovae inter animalia, nemo consecrabit: sive bos, sive ovis, Jehovae est.