Numbers 3:39-43

3:39 All who were numbered of the Levites, whom Moses and Aaron numbered by the word of the Lord, according to their families, every male from a month old and upward, were 22,000.

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.