Leviticus 27:9-10

Redemption of Vowed Animals

27:9 “‘If what is vowed is a kind of animal from which an offering may be presented to the Lord, anything which he gives to the Lord from this kind of animal will be holy. 27:10 He must not replace or exchange it, good for bad or bad for good, and if he does indeed exchange one animal for another animal, then both the original animal and its substitute will be holy.

Leviticus 27:31

27:31 If a man redeems part of his tithe, however, he must add one fifth to it.