John Gill Commentary Joshua 13:23

"And the border of the children of Reuben was the Jordan, and the border [thereof]. This was the inheritance of the children of Reuben according to their families, the cities and the villages thereof." — Joshua 13:23 (ASV)

And the border of the children of Reuben was Jordan, and the
border [thereof]
As their border eastward was Aroer on the river Arnon, so their border westward was the river Jordan:

this [was] the inheritance of the children of Reuben, after their
families, the cities and the villages thereof ;
which Moses gave them on the other side Jordan; and next follow an account of the inheritance of the tribe of Gad in those parts.