Leviticus 27:9-13 - Redemption Of Vowed Animals
9 If the vow is to give the kind of animal that people offer to Jehovah, it will be considered holy. 10 Do not exchange or substitute animals, a good one for a bad one or a bad one for a good one. If you do exchange one animal for another, then both animals will be holy.
11 If it is an unclean animal that cannot be brought to Jehovah as an offering, bring it in front of the priest. 12 The priest will determine what its value is. The value will be whatever the priest decides. 13 If you want to buy it back, you must pay its full value plus one-fifth more.