Leviticus 27:9-13 - Redemption Of Vowed Animals
9 "If it's an animal from which they make an offering to the LORD, everything that he gives to the LORD from it will be holy. 10 He is not to substitute it or exchange it the good with the bad or the bad with the good. If he ever makes an exchange of an animal for an animal, then it and what's being exchanged is holy.
11 If any animal is unclean, which cannot be brought to the LORD as an offering, make the animal stand in the presence of the priest, 12 then the priest will evaluate it as to whether it is good or bad. According to your that is, the priest's valuation, so it is to be. 13 If a kinsman redeemer decides to redeem it, then he is to add a fifth to your valuation."