Numbers 35:12, 21, 24, 27

The cities shall be to you as a refuge from the avenger, so that the one who has caused the death of another will not be killed until he has had a [fair] trial before the congregation.

or if, in enmity, he struck the victim down with his hand, and he died, the one that struck the victim shall certainly be put to death; he is a murderer. The blood avenger shall put the murderer to death when he meets him.

then the congregation shall judge between the offender and the blood avenger according to these ordinances.

and the blood avenger finds him outside the border of his city of refuge and kills the offender, the blood avenger will not be guilty of murder