Deuteronomy 19:4-10

“If someone kills another person unintentionally, without previous hostility, the slayer may flee to any of these cities to live in safety. For example, suppose someone goes into the forest with a neighbor to cut wood. And suppose one of them swings an ax to chop down a tree, and the ax head flies off the handle, killing the other person. In such cases, the slayer may flee to one of the cities of refuge to live in safety. “If the distance to the nearest city of refuge is too far, an enraged avenger might be able to chase down and kill the person who caused the death. Then the slayer would die unfairly, since he had never shown hostility toward the person who died. That is why I am commanding you to set aside three cities of refuge. “And if the LORD your God enlarges your territory, as he swore to your ancestors, and gives you all the land he promised them, you must designate three additional cities of refuge. (He will give you this land if you are careful to obey all the commands I have given you—if you always love the LORD your God and walk in his ways.) 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.