Numbers 35:11-15

11designate cities to serve as your cities of refuge, so that a person who kills someone unintentionally may flee there. 12You are to have these cities as a refuge from the avenger, so that the manslayer will not die until he stands trial before the assembly.

13The cities you select will be your six cities of refuge. 14Select three cities across the Jordan and three in the land of Canaan as cities of refuge. 15These six cities will serve as a refuge for the Israelites and for the foreigner or stranger among them, so that anyone who kills a person unintentionally may flee there.