Leviticus 27:30-33 - Redemption Of The Tithe
30 "Any tithes of the land from grain grown on the land or from fruit grown on the trees belong to the LORD. They are sacred to the LORD. 31 But if a person wishes to redeem his tithe, he is to add a fifth to it. 32 All the tithes from cattle and flocks that pass under the measuring rod are sacred to the LORD. 33 He is not to examine it to see if it's good or bad or even exchange it. If he does exchange it, what has been exchanged as well as its substitute is sacred. It is not to be redeemed."