Deuteronomy 19:9-11

9if you keep and carefully observe all these commandments which I am commanding you today, to love the Lord your God, and to walk [that is, to live each and every day] always in His ways—then you shall add three more cities [of refuge] for yourself, besides these three,

10so that innocent blood will not be shed [by blood avengers] in your land which the Lord your God is giving you as an inheritance, and blood guilt will not be on you [for the death of an innocent man].

11“But if there is a man who hates his neighbor and lies in wait and ambush for him and attacks him and strikes him down so that he dies, and the assailant escapes to one of these cities,