Leviticus 27:9

7If the person is from sixty years old and upward; if he is a male, then your valuation shall be fifteen shekels, and for a female ten shekels.

8But if he is poorer than your valuation, then he shall be set before the priest, and the priest shall assign a value to him. The priest shall assign a value according to his ability to pay.

9“‘If it is an animal of which men offer an offering to the LORD, all that any man gives of such to the LORD becomes holy.

10He shall not alter it, nor exchange it, a good for a bad, or a bad for a good. If he shall at all exchange animal for animal, then both it and that for which it is exchanged shall be holy.

11If it is any unclean animal, of which they do not offer as an offering to the LORD, then he shall set the animal before the priest;