Instructions for the Ark

Numbers 7:9 But unto the sons of Kohath he gave none: because the service of the sanctuary belonging unto them [was that] they should bear upon their shoulders.

Through Moses the Lord had given special instruction concerning the transportation of the ark. None but the priests, the descendants of Aaron, were to touch it, or even to look upon it uncovered. . . . {CC 176.2}
The priests were to cover the ark, and then the Kohathites must lift it by the staves, which were placed in rings upon each side of the ark and were never removed. To the Gershonites and Merarites, who had in charge the curtains and boards and pillars of the tabernacle, Moses gave carts and oxen for the transportation of that which was committed to them. "But unto the sons of Kohath he gave none: because the service of the sanctuary belonging unto them was that they should bear upon their shoulders" CC 176.3