Leviticus 27:2

27:2 “Speak to the Israelites and tell them, ‘When a man makes a special votive offering based on the conversion value of persons to the Lord,

Leviticus 27:8

27:8 If he is too poor to pay the conversion value, he must stand the person before the priest and the priest will establish his conversion value; according to what the man who made the vow can afford, the priest will establish his conversion value.