Numbers 3:40-41

40Then the Lord said to Moses, “1Count every firstborn male of the sons of Israel from a month old and upward, and 2make a list of their names.

41And you 3shall take the Levites for Me--I am the Lord--instead of all the firstborn among the sons of Israel; and the cattle of the Levites in place of all the firstborn among the cattle of the sons of Israel.”