Deuteronomy 3:16-17

and to the Reubenites and the Gadites I gave the territory from Gilead as far as the Valley of the Arnon, with the middle of the valley as a border, as far over as the river Jabbok, the border of the Ammonites; the Arabah also, with the Jordan as the border, from Chinnereth as far as the Sea of the Arabah, the Salt Sea, under the slopes of Pisgah on the east.