Leviticus 27:9-13 - Redemption Of Vowed Animals
9 And if it be a beast, of which men offer an oblation to LORD, all that any man gives of such to LORD shall be holy. 10 He 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.
11 And if it be any unclean beast, of which they do not offer an oblation to LORD, then he shall set the beast before the priest, 12 and the priest shall value it, whether it be good or bad. As thou the priest values it, so shall it be. 13 But if he will indeed redeem it, then he shall add the fifth part of it to thy estimation.