Numbers 35:9-15

Then the LORD spoke to Moses, saying, “Speak to the sons of Israel and say to them, ‘When you cross the Jordan into the land of Canaan, then you shall select for yourselves cities to be your cities of refuge, that the manslayer who has killed any person unintentionally may flee there. The cities shall be to you as a refuge from the avenger, so that the manslayer will not die until he stands before the congregation for trial. The cities which you are to give shall be your six cities of refuge. You shall give three cities across the Jordan and three cities in the land of Canaan; they are to be cities of refuge. These six cities shall be for refuge for the sons of Israel, and for the alien and for the sojourner among them; that anyone who kills a person unintentionally may flee there.