Leviticus 27:11-13

27:11 If what is vowed is an unclean animal from which an offering must not be presented to the Lord, then he must stand the animal before the priest, 27:12 and the priest will establish its conversion value, whether good or bad. According to the assessed conversion value of the priest, thus it will be. 27:13 If, however, the person who made the vow redeems the animal, he must add one fifth to its conversion value.