Numbers 3:38-39

38But those that encamp before the tabernacle toward the east, even before the tabernacle of the congregation eastward, shall be Moses, and Aaron and his sons, keeping the charge of the sanctuary for the charge of the children of Israel; and the stranger that cometh nigh shall be put to death. 39All that were numbered of the Levites, which Moses and Aaron numbered at the commandment of the Lord, throughout their families, all the males from a month old and upward, were twenty and two thousand.