Numbers 3:40-42

King James Version

⁴⁰ And the Lord said unto Moses, Number all the firstborn of the males of the children of Israel from a month old and upward, and take the number of their names.

⁴¹ And thou shalt take the Levites for me (I am the Lord) instead of all the firstborn among the children of Israel; and the cattle of the Levites instead of all the firstlings among the cattle of the children of Israel.

⁴² And Moses numbered, as the Lord commanded him, all the firstborn among the children of Israel.