Numbers 35:9-15

And Jehovah spake unto Moses, saying, Speak unto the children of Israel, and say unto them, When ye pass over the Jordan into the land of Canaan, then ye shall appoint you cities to be cities of refuge for you, that the manslayer that killeth any person unwittingly may flee thither. And the cities shall be unto you for refuge from the avenger, that the manslayer die not, until he stand before the congregation for judgment. And the cities which ye shall give shall be for you six cities of refuge. Ye shall give three cities beyond the Jordan, and three cities shall ye give in the land of Canaan; they shall be cities of refuge. For the children of Israel, and for the stranger and for the sojourner among them, shall these six cities be for refuge; that every one that killeth any person unwittingly may flee thither.