Deuteronomy 19:8-10

8“If the Lord your God enlarges your border, as He has sworn to your fathers to do, and gives you all the land which He promised to give to your fathers—

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].