Numbers 2:33

But the Levites were not numbered among the children of Israel; as the LORD commanded Moses.

The census left the Levites unnumbered among the children of Israel, as the Lord commanded Moses. Their exclusion was because God set them apart for sacred service in the center of the camp, giving them a distinct, God-appointed place and duty connected with the tabernacle. Their distinct work was to carry the ark and the tabernacle and its furnishings, to care for the sanctuary, and to perform their own sacred work rather than being assigned indiscriminately to the work of the other tribes, with each person having a particular work assigned. In the march a special family was appointed to carry the sacred ark borne in the midst of the Levites, with Moses and Aaron marching just in front of the ark and the sons of Aaron following near them bearing trumpets to signify directions to the people.

The exception was part of the perfect order God required and commanded for all pitching and journeying in all the wilderness travels. Every other tribe carried its distinguishing standard with the sign of its father's house upon it and was commanded to pitch under its own standard by its own standard and to march in order under its own standard. While Israel lived in tents the tribes pitched in their commanded positions in order in just the position God commanded around the tabernacle at a distance from it, and the tabernacle was erected when they rested. They abode in camp pitching their tents when the pillar of cloud and glory rested low over the tabernacle, and journeyed with the ark of the covenant borne before them when the cloud was lifted high above the tabernacle, as directed by the understood sounds of the trumpets.

This arrangement of the camp with its order and arrangements around the tabernacle was for the benefit of Israel and was designed to impress Israel and the surrounding nations with God's majesty and holiness and government, showing the purity and order He desires in those who serve Him and that the Lord governed Israel. The orderly arrangement shows that God values order and does not approve confusion in His work. He remains the same God of order in the present dispensation as in the former, as particular now as then, and Israel was to follow the order He appointed. The faithful record of wilderness deliverance and organization together with sin, rebellion, and punishment is hung up as a warning written for the admonition of those on whom the ends of the world come, lest they follow the example of disobedience and fall, that we should learn lessons of order and organization from the perfect organization and special order instituted in the days of Moses for the benefit of the children of Israel.