Numbers 3:38
But 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.
Moses with Aaron and Aaron's sons encamped in front of the tabernacle toward the east, eastward of the tabernacle of the congregation. They kept the charge of the sanctuary for the charge of the children of Israel, guarding it on behalf of the people. The Levites had responsibility for the tabernacle and everything connected with it, taking it down when the camp moved and setting it up again at each stopping place.
No one not appointed was permitted to come near the sanctuary, and no one from another tribe was permitted to approach it. Any unauthorized person who came near was to be put to death. Sacred duties and access to the sanctuary were thus assigned to specific appointed people.