Leviticus 27:9-13 - Redemption Of Vowed Animals
9 'Now if it is an animal of the kind which men can present as an offering to the LORD, any such that one gives to the LORD shall be holy. 10 'He shall not replace it or exchange it, a good for a bad, or a bad for a good; or if he does exchange animal for animal, then both it and its substitute shall become holy.
11 'If, however, it is any unclean animal of the kind which men do not present as an offering to the LORD, then he shall place the animal before the priest. 12 'The priest shall value it as either good or bad; as you, the priest, value it, so it shall be. 13 'But if he should ever wish to redeem it, then he shall add one-fifth of it to your valuation.