Numbers 3:41-45
41 You are to take the Levites for Me—I am Yahweh—in place of every firstborn among the Israelites, and the Levites’ cattle in place of every firstborn among the Israelites’ cattle.”
42 So Moses registered every firstborn among the Israelites, as the Lord commanded him.
43 The total number of the firstborn males one month old or more listed by name was 22,273.