A City of Refuge were a cities in Israel specially designated to act as a safe haven for those guilty of accidental murder. A man wrongfully accused of murder, would be allowed to take refuge in one of these cities, from anyone attempting to avenge the death. The accused would then undergo trial conducted by the city's elders and if judged innocent would live in this city until the current High Priest died. In the case that the refugee was guilty, they would be put to death. Any attempt of harm by an avenger to a refugee would be deemed as a crime, and if murder would be punishable by death.
These six cities would be alloted to and under the administration of the Tribe of Levi, but were located within the territorial confines of specific tribes. Spread across Israel, the cities of refuge were located in close enough distance to the population where someone could reasonably hide their from a pursuer. Originally there were to be three refugee cities, in Canaan, but after Israel's territory expanded west of the Jordan River three additional cities were designated.
At one point, Israel was camped in the plains of Moab across from the Jordan river adjacent to Jericho. During this time, God gave Moses revelation of various laws, including those regarding the establishment of a refuge city program. When Israel crossed into Canaan they should designate three cities, based on their proximity to the rest of Israel in order to make them easily accessible by anyone. Each of these cities would serve as a sanctuary city for any person accused of murder, who was innocent from an avenging assailant. If God, expanded the territory across the Jordan than three additional cities would need to be designated.