6 If a person is from one month to five years old, then your valuation for a male is to be five shekels of silver, and for a female your valuation is to be three shekels of silver.
Leviticus 27:6 Cross References - ISV
Numbers 3:40-43
40 Numbering Israel’s First-bornLater the LORD instructed Moses: “Number all the first-born males of Israel from a month old and above and list their names.
41 Separate the descendants of Levi for me—since I am the LORD—in place of all the first-born sons of Israel. Also separate the livestock of the descendants of Levi in place of all the firstborn of the livestock of Israel.”
42 So Moses numbered all the firstborn from the sons of Israel just as the LORD commanded him.
43 All the first-born males according to the list of their names from a month old and above numbered 22,273.
Numbers 18:14-16
14 Every devoted thing in Israel is yours, too.
15 Everything that opens the womb, any living thing that they bring to the LORD—whether from human beings or animals—are for you. Just be sure that you redeem the firstborn of people and the firstborn of unclean animals.
16 Those that can be redeemed, you are to redeem at the age of one month, based on your estimate—for five shekels of silver, according to the shekel of the sanctuary, that is, for 20 gerahs.