Leviticus 27:8-12

⁸But if he shall be poorer than thy estimation, then he shall present himself before the priest, and the priest shall value him: according to his ability that vowed shall the priest value him.

⁹And if it shall be a beast of which men bring an offering to the LORD, all that any man giveth of such to the LORD 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 it and the exchange of it shall be holy.

¹¹And if it shall be any unclean beast, of which they do not offer a sacrifice to the LORD, then he shall present the beast before the priest:

¹²And the priest shall value it, whether it be good or bad: as thou valuest it, who art the priest, so shall it be.