Deuteronomy 19:2-4

Complete Jewish Bible

² you are to set aside three cities for yourselves in your land that Adonai your God is giving you to possess. 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.