John Gill Commentary Joshua 18:7

"For the Levites have no portion among you; for the priesthood of Jehovah is their inheritance: and Gad and Reuben and the half-tribe of Manasseh have received their inheritance beyond the Jordan eastward, which Moses the servant of Jehovah gave them." — Joshua 18:7 (ASV)

But the Levites have no part among you
And so needed not to send any men out of their tribe to measure the land on their account, and is a reason why the remaining part of the land was to be divided into seven parts only:

for the priesthood of the Lord [is] his inheritance ;
not only the office, but what appertained to it, all the perquisites of it, the tithes, firstfruits, parts of the sacrifices see (Joshua 13:14) ;

and Gad, and Reuben, and half the tribe of Manasseh, have received
their inheritance beyond Jordan on the east, which Moses the servant of
the Lord gave them ;
and so had no share in the division of the land of Canaan, being sufficiently provided for.