John Calvin Commentary Deuteronomy 23:18

"Thou shalt not bring the hire of a harlot, or the wages of a dog, into the house of Jehovah thy God for any vow: for even both these are an abomination unto Jehovah thy God." — Deuteronomy 23:18 (ASV)

You shall not bring the hire. This command is related to the preceding one, for God, by rejecting whatever is acquired by illicit and sordid dealings, teaches us that the utmost purity must be observed in sacred things; He not only refuses the payment for a prostitute, but also the price of a dog, so that the sanctity of the altar would not be polluted by any impure offering. However, the dog seems to be rejected in comparison with other animals out of contempt; for it was just as wrong to kill a pig as a dog, yet the price of a pig could be offered. The dog, therefore, is rejected not only as an unclean animal, but also as vile and contemptible. In summary, God intended to impress upon them the reverence owed to His temple and altar.