John Gill Commentary Numbers 7:2

"that the princes of Israel, the heads of their fathers` houses, offered. These were the princes of the tribes, these are they that were over them that were numbered:" — Numbers 7:2 (ASV)

That the princes of Israel
The princes of the twelve tribes of Israel:

heads of the house of their fathers ;
of each of the houses and families the tribes were divided into, and took their name from each of their ancestors, as is next explained:

who were princes of the tribes ;
the twelve tribes, as before observed, (Numbers 1:4–16) ;

and were over them that were numbered ;
over the children of Israel that were numbered, (Numbers 1:19–46) ; by which it that these princes are the very same persons that are mentioned by name there, as they are here afterwards; and were with Moses and Aaron, and assisting to them when they took the number of them; but according to the Targum of Jonathan, and Jarchi, these were appointed over them in Egypt; but the former is right: these now

offered
not sacrifices but gifts; they brought their presents to the Lord for the service of his sanctuary, and set them before him, as follows.