Numbers 35:11-15

11then you shall select for yourselves cities to be cities of refuge, so that the one who kills any person unintentionally may escape there.

12The cities shall be to you as a refuge from the avenger, so that the one who has caused the death of another will not be killed until he has had a [fair] trial before the congregation.

13The cities which you are to provide shall be your six cities of refuge.

14You shall provide three cities on this [east] side of the Jordan [River], and three [more] cities in the land of Canaan; they are to be the cities of refuge.

15These six cities shall be a refuge for the Israelites and for the stranger and the resident alien among them; so that anyone who kills a person unintentionally may escape there.