Deuteronomy 19:2-4

Contemporary English Version

^2-4 you must choose three of your towns to be Safe Towns. Divide the land into three regions with one Safe Town near the middle of each, so that a Safe Town can be easily reached from anywhere in your land.

Then, if one of you accidentally kills someone, you can run to a Safe Town and find protection from being put to death. But you must not have been angry with the person you killed.