Leviticus 27:8-10

Modern English Version

⁸ But if he is too poor to afford the equivalent value, then he shall present himself before the priest and the priest shall set his value. According to what the person making the vow can afford, so the priest shall set his value.

⁹ And if it be an animal, of which men bring an offering to the Lord, all that any man gives of such to the Lord shall be holy. ¹⁰ He shall not exchange it nor substitute it, good for bad or bad for good. If he in fact substitutes an animal for another, then both it and its substitute shall be holy.