Numbers 4:49
According to the commandment of the LORD they were numbered by the hand of Moses, every one according to his service, and according to his burden: thus were they numbered of him, as the LORD commanded Moses. According to the commandment of the LORD they were numbered by the hand of Moses, every one according to his service, and according to his burden: thus were they numbered of him, as the LORD commanded Moses.
The numbering according to service and burden concerned the Levites and their appointed duties in connection with the tabernacle. They were the ones who erected the tabernacle and encamped around it to guard and attend it. When Israel journeyed they took the tabernacle down and carried it forward with its sacred furnishings.
This assigned service was bestowed as an honor from God. It was given in recognition of their faithfulness at the time of the golden calf, when they took no part in making it or in worshiping it.