Deuteronomy 4:46-48

46At that time they were in the valley near to Beth-Peor, on the east side of the Jordan River. That was in the land of Sihon, king of the Amorites, who ruled in Heshbon. Moses and the Israelites had attacked him after they came out of Egypt.

47They took power over his land, as well as the land of Og, king of Bashan. These two Amorite kings ruled on the east side of the Jordan River.

48Their land went from Aroer, on the edge of the Arnon valley, as far as Mount Sirion (that is Mount Hermon).