Leviticus 27:6

2 “Speak to the Israelites and say to them, ‘When someone makes a special vow to the LORD involving the value of persons,

3 if the valuation concerns a male from twenty to sixty years of age, then your valuation shall be fifty shekels of silver, according to the sanctuary shekel.

4 Or if it is a female, then your valuation shall be thirty shekels.

5 And if the person is from five to twenty years of age, then your valuation for the male shall be twenty shekels, and for the female ten shekels.

6 Now if the person is from one month to five years of age, then your valuation for the male shall be five shekels of silver, and for the female three shekels of silver.

7 And if the person is sixty years of age or older, then your valuation shall be fifteen shekels for the male and ten shekels for the female.

8 But if the one making the vow is too poor to pay the valuation, he is to present the person before the priest, who shall set the value according to what the one making the vow can afford.

9 If he vows an animal that may be brought as an offering to the LORD, any such animal given to the LORD shall be holy.

10 He must not replace it or exchange it, either good for bad or bad for good. But if he does substitute one animal for another, both that animal and its substitute will be holy.

Read all of Leviticus 27