Deuteronomy 19:3-5

Complete Jewish Bible

³ Divide the territory of your land, which Adonai your God is having you inherit, into three parts; and prepare the roads, so that any killer can flee to these cities. ⁴ The killer who will live if he flees there is someone who has killed his fellow member of the community by mistake, who did not hate him in the past. ⁵ An example would be if a man goes into the forest with his neighbor to cut wood and takes a stroke with the axe to fell a tree, but the head of the axe flies off the handle, hits his neighbor and kills him. Then he is to flee to one of these cities and live there.