Deuteronomy 4:41-49

Then Moses set apart three cities across the Jordan to the east, that a manslayer might flee there, who unintentionally slew his neighbor without having enmity toward him in time past; and by fleeing to one of these cities he might live: Bezer in the wilderness on the plateau for the Reubenites, and Ramoth in Gilead for the Gadites, and Golan in Bashan for the Manassites. Now this is the law which Moses set before the sons of Israel; these are the testimonies and the statutes and the ordinances which Moses spoke to the sons of Israel, when they came out from Egypt, across the Jordan, in the valley opposite Beth-peor, in the land of Sihon king of the Amorites who lived at Heshbon, whom Moses and the sons of Israel defeated when they came out from Egypt. They took possession of his land and the land of Og king of Bashan, the two kings of the Amorites, who were across the Jordan to the east, from Aroer, which is on the edge of the valley of Arnon, even as far as Mount Sion (that is, Hermon), with all the Arabah across the Jordan to the east, even as far as the sea of the Arabah, at the foot of the slopes of Pisgah.