John Gill Commentary Joshua 21:16

"and Ain with its suburbs, and Juttah with its suburbs, [and] Beth-shemesh with its suburbs; nine cities out of those two tribes." — Joshua 21:16 (ASV)

And Ain with her suburbs (See Gill on Joshua 15:32); and Juttah with her suburbs; (See Gill on Joshua 15:55); [and] Bethshemesh with her suburbs ;
which is not mentioned among the cities of Judah, (Joshua 15:21–63) ; only as in the borders of it, (Joshua 21:10) ; and perhaps is the same Bethshemesh to which the ark was directed by the Philistines from Ashdod, (1 Samuel 6:9 1 Samuel 6:12) ; in it formerly was a temple dedicated to the sun, from whence it had its name: nine cities out of those two tribes ;
and they seem all but one, which is Ain, to be of the tribe of Judah, and that originally belonged to it; and as that tribe had the largest number of cities in its lot, the more were given out of it to the Levites, according to a rule prescribed, (Numbers 35:8) .