Numbers 3:38-39

38Moses, Aaron, and his sons put up their tents on the east side in front of the tent of meeting. They were in charge of the holy place on behalf of the Israelites. Anyone else who tried to do the Levites’ duties had to be put to death.

39The grand total of Levites that Moses and Aaron counted at the Lord’s command, by families, every male who was at least one month old, was 22,000.