Numbers 1:52-56

So the sons of Israel shall camp, each man by his own camp, and each man by his own flag, according to their armies.

But the Levites shall camp around the tabernacle of the testimony, so that there will be no divine wrath against the congregation of the sons of Israel. So the Levites shall be responsible for service to the tabernacle of the testimony.”

And the sons of Israel did so; in accordance with all that the Lord had commanded Moses, so they did.