Numbers 3:40-45

40And the LORD said to 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. 41And 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. 42And Moses numbered, as the LORD commanded him, all the firstborn among the children of Israel. 43And all the firstborn males by the number of names, from a month old and upward, of those that were numbered of them, were twenty and two thousand two hundred and seventy and three. 44And the LORD spoke to Moses, saying, 45Take the Levites instead of all the firstborn among the children of Israel, and the cattle of the Levites instead of their cattle; and the Levites shall be mine: I am the LORD.