John Gill Commentary 1 Chronicles 15

And David made him houses in the city of David
With the help of the masons and carpenters Hiram sent him, (1 Chronicles 14:1) , the royal palace is meant, with all the apartments in it, which were many and large, as so great a family he had required, and with all the out houses to it necessary for his servants, and their offices:

and prepared a place for the ark of God, and pitched for it a tent ;
see (2 Samuel 6:17) .

Then David said
Either within himself, or to his ministers and courtiers about him:

none ought to carry the ark of God but the Levites ;
he saw his former mistake in employing those that were not Levites in bringing up the ark from Kirjathjearim, and bringing it in a cart, and not on the shoulders of the Levites, and so miscarried in his attempt, (2 Samuel 6:1) and, perhaps, had since more diligently consulted the law of God about this matter:

for them has the Lord chosen to carry the ark of God, and to minister
unto him for ever ;
as long as the Levitical dispensation lasted, as appears from (Numbers 1:50) (4:15) (7:9) .

And David gathered all Israel together to Jerusalem
The chief and heads of the people:

to bring up the ark of the Lord ;
from the house of Obededom, where it had been three months, and for the sake of which his house was blessed, and which David heard of; and this encouraged him to take this step to fetch it from thence: unto his place, which he had prepared for it; (1 Chronicles 15:1) (2 Samuel 6:12 2 Samuel 6:17) .

] Whose business it was to bear the ark when there was any occasion for it: and from hence to the end of (1 Chronicles 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 sons, and so those of the rest after mentioned, had been dead ages ago; the principal of those, at this present time, was Uriel, and his kindred, or those of the same family with him, were one hundred and twenty:

of those of Merari, another son of Levi, the chief was Asaiah, with two hundred and twenty of his relations:

of those of Gershon, another son of Levi, was Joel, and his brethren were one hundred and thirty:

of the posterity of Elizaphan, a grandson of Kohath, (Exodus 5:18Exodus 5:22) , the most noted was Shemaiah, who had two hundred of his family with him:

and of those of Hebron, the son of Kohath, (Exodus 6:18) , Eliel was the most famous, and he had eighty of his kindred with him:

and of those of Uzziel, another son of Kohath in a different line from Elizaphan, who also was a son of Uzziel, was Amminadab the chief, who had one hundred and twelve of his kindred with him: the number of Levites, in all, gathered together, were eight hundred and sixty two, besides their chiefs.

(See Gill on 1 Chronicles 15:4).