The Levites are to camp around the Tabernacle of the Testimony, so that there will be no wrath unleashed on the community of Bnei-Yisrael. So the Levites are to maintain care of the Tabernacle of the Testimony.
Those 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.
He may assist his brothers in the Tent of Meeting to do their duties, but he himself will no longer do the work. Thus, you are to assign to the Levites their responsibilities.”