Leviticus 27:9-13

9‘If it is an animal that men may bring as an offering to the Lord, all that anyone gives to the Lord shall be holy.

10He shall not substitute it or exchange it, good for bad or bad for good; and if he at all exchanges animal for animal, then both it and the one exchanged for it shall be holy.

11If it is an unclean animal which they do not offer as a sacrifice to the Lord, then he shall present the animal before the priest;

12and the priest shall set a value for it, whether it is good or bad; as you, the priest, value it, so it shall be.

13But if he wants at all to redeem it, then he must add one-fifth to your valuation.