Deuteronomy 4:41-43

Then Moses set apart three cities of refuge east of the Jordan River. Anyone who killed another person unintentionally, without previous hostility, could flee there to live in safety. These were the cities: Bezer on the wilderness plateau for the tribe of Reuben; Ramoth in Gilead for the tribe of Gad; Golan in Bashan for the tribe of Manasseh.