Leviticus 27:30-33

30“One-tenth of what comes from the land, whether grain or fruit, is holy and belongs to the Lord.

31If you buy back any part of it, you must add one-fifth more to it.

32Every tenth head of cattle or sheep that you counted is holy and belongs to the Lord.

33You must not look to see if it is good or bad or exchange it. But if you do exchange it, both the first animal and its substitute will be holy. They cannot be bought back.”