Deuteronomy 19:10-12

That way you will prevent the death of innocent people in the land the LORD your God is giving you as your special possession. You will not be held responsible for the death of innocent people. “But suppose someone is hostile toward a neighbor and deliberately ambushes and murders him and then flees to one of the cities of refuge. In that case, the elders of the murderer’s hometown must send agents to the city of refuge to bring him back and hand him over to the dead person’s avenger to be put to death.