Because of the sanctuary, &c. The Seventy translate it more literally, Because they have the service of the holy things, (that is, of the ark, Numbers 4:5; Numbers 4:15.) They shall carry it upon their shoulders This way of carrying the ark was both for greater dignity, on account of the superior holiness and value of it, and its contents and appurtenances, and that the structure of it might not be discomposed, as it might have been by the shaking of a wagon.
Related Commentaries of Numbers 7:9
Numbers 7:9
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.