Numbers 35:12, 21, 24, 27

The cities shall be for you a refuge from the avenger, that the manslayer may not die until he stands before the congregation for judgment.

or in enmity struck him down with his hand, so that he died, then he who struck the blow shall be put to death. He is a murderer. The avenger of blood shall put the murderer to death when he meets him.

then the congregation shall judge between the manslayer and the avenger of blood, in accordance with these rules.

and the avenger of blood finds him outside the boundaries of his city of refuge, and the avenger of blood kills the manslayer, he shall not be guilty of blood.