Deuteronomy 4:41-43

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.