Deuteronomy 4:41-43

Then Moses set apart three cities on this side of the Jordan, toward the rising of the sun, that the manslayer might flee there, who kills his neighbor unintentionally, without having hated him in time past, and that by fleeing to one of these cities he might live: Bezer in the wilderness on the plateau for the Reubenites, Ramoth in Gilead for the Gadites, and Golan in Bashan for the Manassites.