Numbers 35:12-15

121The cities shall 2serve you as a refuge from the avenger, so that the one who commits manslaughter does not die until he stands before the congregation for 3trial. 13So the cities which you are to provide shall be six cities of refuge for you. 14You 4shall provide three cities across the Jordan, and three cities 5in the land of Canaan; they are to be cities of refuge. 15These six cities shall be a refuge for the sons of Israel, for the stranger, and for the foreign resident among them; so that anyone who 6kills a person 7unintentionally may flee there.