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.
But unto the sons of Kohath he gave none,.... Being all disposed of to the sons of Gershon and Merari: the reason of which follows,
because the service of the sanctuary belonging unto them was that they should bear upon their shoulders; as the ark with the mercy seat, and cherubim, the shewbread table, the candlestick, and the two altars; though in later times we find the ark was sometimes not only carried by the priests, but upon a cart, Joshua 3:17.