John Gill Commentary Joshua 21:21

"And they gave them Shechem with its suburbs in the hill-country of Ephraim, the city of refuge for the manslayer, and Gezer with its suburbs," — Joshua 21:21 (ASV)

For they gave them Shechem, with her suburbs, in Mount
Ephraim
Of which see (Joshua 20:7) ; [to be] a city of refuge for the slayer ;
which being on a mountain, was the more conspicuous, and the fitter for this purpose, as was Hebron in the hill country of Judea, (Joshua 21:11Joshua 21:13) ; this is the second; city of refuge mentioned: and Gezer with her suburbs :
a place from which the Canaanites were not expelled; (See Gill on Joshua 16:10).