Then he gathered together the descendants of Aaron and the Levites:
Preparation is here made for the bringing of the ark home to the city of David from the house of Obed-edom. It is here owned that in the former attempt, though it was a very good work and in it they sought God, yet they sought him, not after the due order, Ch1 15:13.
Commenting on 1 Chronicles 15:1-24
And David assembled the children of Aaron, and the Levites. Whose business it was to bear the ark when there was any occasion for it: and from hence to the end of Ch1 15:10 an account is given of the Levites, and their number employed in this affair: of the sons of Kohath; a son of Levi, that is, of his posterity; for his immediate...
David assembled the children of Aaron, and the Levites--The children of Aaron were the two priests (Ch1 15:11), Zadok and Abiathar, heads of the two priestly houses of Eleazar and Ithamar, and colleagues in the high priesthood (Sa2 20:25). The Levites were the chiefs of their father's house (Ch1 15:12); four belonging to the Kohathite branch, on whose shoulders the ark was to be borne...