Leviticus 27:9-13 - Redemption Of Vowed Animals
9 "'If it is an animal, of which men offer an offering to the LORD, all that any man gives of such to the LORD becomes holy. 10 He shall not alter it, nor change it, a good for a bad, or a bad for a good: and if he shall at all change animal for animal, then both it and that for which it is changed shall be holy.
11 If it is any unclean animal, of which they do not offer as an offering to the LORD, then he shall set the animal before the priest; 12 and the priest shall value it, whether it is good or bad. As you the priest values it, so shall it be. 13 But if he will indeed redeem it, then he shall add the fifth part of it to its valuation.