Leviticus 27:9-13

9And if it be a beast, whereof men offer an oblation unto Jehovah, all that any man giveth of such unto Jehovah shall be holy. 10He shall not alter it, nor change it, a good for a bad, or a bad for a good: and if he shall at all change beast for beast, then both it and that for which it is changed shall be holy. 11And if it be any unclean beast, of which they do not offer an oblation unto Jehovah, then he shall set the beast before the priest; 12and the priest shall value it, whether it be good or bad: as thou the priest valuest it, so shall it be. 13But if he will indeed redeem it, then he shall add the fifth part thereof unto thy estimation.