Numbers 3:37-41

and the pillars around the courtyard with their bases, their pegs, and their ropes.

Now those who were to camp in front of the tabernacle eastward, in front of the tent of meeting toward the sunrise, were Moses and Aaron and his sons, performing the duties of the sanctuary for the obligation of the sons of Israel; but the layman coming near was to be put to death.

All the numbered men of the Levites, whom Moses and Aaron counted at the command of the Lord by their families, every male from a month old and upward, were twenty-two thousand. Firstborn Redeemed

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

And you shall 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.”