Deuteronomy 4:41-49

Then Moses set aside three cities east of the Jordan, to which anyone who had killed a person could flee if they had unintentionally killed a neighbor without malice aforethought. They could flee into one of these cities and save their life. The cities were these: Bezer in the wilderness plateau, for the Reubenites; Ramoth in Gilead, for the Gadites; and Golan in Bashan, for the Manassites. This is the law Moses set before the Israelites. These are the stipulations, decrees and laws Moses gave them when they came out of Egypt and were in the valley near Beth Peor east of the Jordan, in the land of Sihon king of the Amorites, who reigned in Heshbon and was defeated by Moses and the Israelites as they came out of Egypt. They took possession of his land and the land of Og king of Bashan, the two Amorite kings east of the Jordan. This land extended from Aroer on the rim of the Arnon Gorge to Mount Sirion (that is, Hermon), and included all the Arabah east of the Jordan, as far as the Dead Sea, below the slopes of Pisgah.