Leviticus 27:26-29

26“But no one can consecrate a firstborn of the livestock, whether an animal from the herd or flock, to the Lord, because a firstborn already belongs to the Lord.

27If it is one of the unclean livestock, it can be ransomed according to your assessment by adding a fifth of its value to it. If it is not redeemed, it can be sold according to your assessment.

28“Nothing that a man permanently sets apart to the Lord from all he owns, whether a person, an animal, or his inherited landholding, can be sold or redeemed; everything set apart is especially holy to the Lord.

29No person who has been set apart for destruction is to be ransomed; he must be put to death.