Leviticus 27:8-12

⁸But if he be too poor for thy valuation, then he shall be set before the priest, and the priest shall value him; according to the means of him that vowed shall the priest value him.

⁹And if it be a beast, whereof men bring an offering unto the LORD, all that any man giveth of such unto 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 both it and that for which it is changed shall be holy.

¹¹And if it be any unclean beast, of which they may not bring an offering unto the LORD, 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.