Leviticus 27:26-28

Amplified Bible

²⁶ ‘However, the firstborn among animals, which as a firstborn belongs to the Lord, no man may consecrate, whether an ox or a sheep. It is [already] the Lord’s. ²⁷ If it is among the unclean animals, the owner may redeem it in accordance with your valuation, and add one-fifth to it; or if it is not redeemed, then it shall be sold in accordance with your valuation.

²⁸ ‘But nothing that a man ^[a]sets apart [that is, devotes as an offering] to the Lord out of all that he has, of man or of animal or of the fields of his own property, shall be sold or redeemed. Anything devoted to destruction (banned, cursed) is most holy to the Lord.