Leviticus 27:30-33

All tenth-part gifts from the land, whether of seed from the ground or fruit from the trees, belong to the LORD; they are holy to the LORD. If someone wishes to buy back part of their tenth-part gift, they must add one-fifth to it. All tenth-part gifts from a herd or flock—every tenth animal that passes under the shepherd’s staff—will be holy to the LORD. The one bringing the tenth-part gift must not pick out the good from the bad, and cannot substitute any animal. But if one should substitute an animal, both it and the substitute will be holy and cannot be bought back.