Numbers 35:8-13
English Standard Version
9And the Lord spoke to Moses, saying,
10"Speak to the people of Israel and say to them, When you cross the Jordan into the land of Canaan,
11then you shall select cities to be cities of refuge for you, that the manslayer who kills any person without intent may flee there.
12The cities shall be for you a refuge from the avenger, that the manslayer may not die until he stands before the congregation for judgment.
13And the cities that you give shall be your six cities of refuge.