Leviticus 27:8-10

New Revised Standard Version Catholic Edition

⁸ If any cannot afford the equivalent, they shall be brought before the priest and the priest shall assess them; the priest shall assess them according to what each one making a vow can afford.

⁹ If it concerns an animal that may be brought as an offering to the Lord, any such that may be given to the Lord shall be holy. ¹⁰ Another shall not be exchanged or substituted for it, either good for bad or bad for good; and if one animal is substituted for another, both that one and its substitute shall be holy.