Numbers 3:7
And they shall keep his charge, and the charge of the whole congregation before the tabernacle of the congregation, to do the service of the tabernacle. And they shall keep his charge, and the charge of the whole congregation before the tabernacle of the congregation, to do the service of the tabernacle.
The Levites were assigned to keep the charge of Aaron and of the whole congregation before the tabernacle of the congregation, and to perform its service there on their behalf. This work belonged to designated people and was to be carried out in the order God appointed, with the tabernacle and its duties not to be handled indiscriminately by others. Their assigned work included caring for the tabernacle, erecting it, and when Israel traveled taking it down and carrying it with its sacred furnishings.
Their service included helping carry out the congregation's worship at the tabernacle. God honored the Levites with this work because they had remained faithful during the golden-calf apostasy and had carried out His command against the idolaters. That Levitical service did not confer the priesthood or authority to claim higher office, since the priesthood was a different office given to Aaron and his family.
Korah illustrates this distinction, for though as a Kohathite Levite he had been appointed to tabernacle service, he was dissatisfied with that role and sought the priesthood. Elkanah illustrates devotion to this charge, for as a Levite he was especially devoted to tabernacle service at a time when worship at Shiloh had become irregular and incomplete.