John Gill Commentary Deuteronomy 4:49

"and all the Arabah beyond the Jordan eastward, even unto the sea of the Arabah, under the slopes of Pisgah." — Deuteronomy 4:49 (ASV)

And all the plain on this side Jordan eastward
The plains of Moab, on that side of Jordan to the east:

even unto the sea of the plain ;
the sea of Sodom, the salt sea:

under the springs of Pisgah ;
that rose from Mount Pisgah, the same with Ashdothpisgah, (Deuteronomy 3:17) .