John Gill Commentary 1 Chronicles 13:2

"And David said unto all the assembly of Israel, If it seem good unto you, and if it be of Jehovah our God, let us send abroad every where unto our brethren that are left in all the land of Israel, with whom the priests and Levites are in their cities that have suburbs, that they may gather themselves unto us;" — 1 Chronicles 13:2 (ASV)

And David said to all the congregation of Israel
To the above persons, as representatives of it:

if it seem good to you, and that it be of the Lord our God ;
if it could be thought by them a good and useful thing, and agreeable to the will of God, and would make for his glory:

let us send abroad to our brethren everywhere that are left in all
the land of Israel ;
that were not then present with them, even all the common people; whom David, though king, owns as his brethren; nor is his antitype ashamed to own this relation between him and his people, (Hebrews 2:11)

and with them also to the priests and Levites which are in their
cities and suburbs :
given to them in the several tribes to dwell in, see (1 Chronicles 6:54–81) ,

that they may gather themselves to us ;
at a certain time and place appointed.