Deuteronomy 19:10-12

so that innocent people will not be killed in your land, the land that the LORD your God is giving you as your own. By doing this you will not be guilty of allowing the death of innocent people. But if a person hates his neighbor and, after hiding and waiting, attacks and kills him and then runs to one of these cities for safety, the elders of his own city should send for the murderer. They should bring the person back from the city of safety and hand him over to the relative who has the duty of punishing the murderer.