Numbers 3:38-39

38Those camping in front of the Tent of Meeting, on the east, toward the sunrise, were Moses, Aaron, and his sons. They were to care for the Sanctuary on behalf of Bnei-Yisrael. But anyone unauthorized who approached had to be executed.

39All the Levites counted by Moses and Aaron at the word of Adonai, by their families, inclusive of every male one month old and upward, were 22,000.