Numbers 3:40

³⁸They that encamp before the tabernacle of witness on the east shall be Moses and Aaron and his sons, keeping the charges of the sanctuary according to the charges of the children of Israel; and the stranger that touches them, shall die.

³⁹All the numbering 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 two and twenty thousand.

— Numbers 3:40 —

⁴¹And thou shalt take the Levites for me—I am the Lord—instead of all the firstborn of the sons of Israel, and the cattle of the Levites instead of all the firstborn among the cattle of the children of Israel.

⁴²And Moses counted, as the Lord commanded him, every firstborn among the children of Israel.