Numbers 35:12-19

12You are to have these cities as a refuge from the avenger, so that the manslayer will not die until he stands trial before the assembly.

13The cities you select will be your six cities of refuge. 14Select three cities across the Jordan and three in the land of Canaan as cities of refuge. 15These six cities will serve as a refuge for the Israelites and for the foreigner or stranger among them, so that anyone who kills a person unintentionally may flee there.

16If, however, anyone strikes a person with an iron object and kills him, he is a murderer; the murderer must surely be put to death. 17Or if anyone has in his hand a stone of deadly size, and he strikes and kills another, he is a murderer; the murderer must surely be put to death. 18If anyone has in his hand a deadly object of wood, and he strikes and kills another, he is a murderer; the murderer must surely be put to death.

19The avenger of blood is to put the murderer to death; when he finds him, he is to kill him.