Numbers 1:44-54

These were the men registered by Moses and Aaron and the twelve leaders of Israel, all listed according to their ancestral descent. They were registered by families—all the men of Israel who were twenty years old or older and able to go to war. The total number was 603,550. But this total did not include the Levites. For the LORD had said to Moses, “Do not include the tribe of Levi in the registration; do not count them with the rest of the Israelites. Put the Levites in charge of the Tabernacle of the Covenant, along with all its furnishings and equipment. They must carry the Tabernacle and all its furnishings as you travel, and they must take care of it and camp around it. Whenever it is time for the Tabernacle to move, the Levites will take it down. And when it is time to stop, they will set it up again. But any unauthorized person who goes too near the Tabernacle must be put to death. Each tribe of Israel will camp in a designated area with its own family banner. But the Levites will camp around the Tabernacle of the Covenant to protect the community of Israel from the LORD’s anger. The Levites are responsible to stand guard around the Tabernacle.” So the Israelites did everything just as the LORD had commanded Moses.