Leviticus 27:1-3

Again, the LORD spoke to Moses, saying, “Speak to the children of Israel and say to them, ‘When a man makes a special vow [consecrating himself or a member of his family], he shall be valued according to your [established system of] valuation of people belonging to the LORD [that is, the priest accepts from the man making the vow a specified amount of money for the temple treasury in place of the actual person]. If your valuation is of a male between twenty and sixty years of age, then your valuation shall be fifty shekels of silver, according to the shekel of the sanctuary.