Numbers 3:31
And their charge shall be the ark, and the table, and the candlestick, and the altars, and the vessels of the sanctuary wherewith they minister, and the hanging, and all the service thereof. And their charge shall be the ark, and the table, and the candlestick, and the altars, and the vessels of the sanctuary wherewith they minister, and the hanging, and all the service thereof.
The charge laid out here belongs to the Kohathites, giving them responsibility for the ark together with the other furnishings and vessels of the tabernacle. That trust made them custodians of the sanctuary's most sacred objects, to be cared for as their appointed share in the Levites' service to the tabernacle. Their stewardship extended to the altars and to the implements with which ministry was performed in the sanctuary service.
The Kohathites camped on the south side of the tabernacle. Their assigned care was separate and distinct from the duties appointed to the Gershonites and to the Merarites.