Numbers 3:40-43

The Substitution for the Firstborn

3:40 Then the Lord said to Moses, “Number all the firstborn males of the Israelites from a month old and upward, and take the number of their names. 3:41 And take the Levites for me – I am the Lord – instead of all the firstborn males among the Israelites, and the livestock of the Levites instead of all the firstborn of the livestock of the Israelites.” 3:42 So Moses numbered all the firstborn males among the Israelites, as the Lord had commanded him. 3:43 And all the firstborn males, by the number of the names from a month old and upward, totaled 22,273.

Numbers 18:14-16

18:14 “Everything devoted in Israel will be yours. 18:15 The firstborn of every womb which they present to the Lord, whether human or animal, will be yours. Nevertheless, the firstborn sons you must redeem, and the firstborn males of unclean animals you must redeem. 18:16 And those that must be redeemed you are to redeem when they are a month old, according to your estimation, for five shekels of silver according to the sanctuary shekel (which is twenty gerahs).