Leviticus 27:30-33 - Redemption Of The Tithe
30 One-tenth of what comes from the land, whether grain or fruit, is holy and belongs to Jehovah. 31 If you buy back any part of it, you must add one-fifth more to it. 32 Every tenth head of cattle or sheep that you counted is holy and belongs to Jehovah. 33 You must not look to see if it is good or bad or exchange it. If you do exchange it, both the first animal and its substitute will be holy. They may not be bought back.'