Deuteronomy 19:2–9

²you shall set apart three cities in the land that the Lord your God is giving you to possess.^{* 3}You shall calculate the distances^x and divide into three regions the land that the Lord your God gives you as a possession, so that any homicide can flee to one of them.

⁴“Now this is the case of a homicide who might flee there and live, that is, someone who has killed another person unintentionally when the two had not been at enmity before.^{* 5}Suppose someone goes into the forest with another to cut wood, and when one of them swings the ax to cut down a tree, the head slips from the handle and strikes the other person, who then dies; the killer may flee to one of these cities and live. ⁶But if the distance is too great, the avenger of blood in hot anger might pursue and overtake and put the killer to death, although a death sentence was not deserved, since the two had not been at enmity before.^{* 7}Therefore I command you: You shall set apart three cities.

⁸“If the Lord your God enlarges your territory, as he swore to your ancestors—and he will give you all the land that he promised your ancestors to give you, ⁹provided you diligently observe this entire commandment that I command you today, by loving the Lord your God and walking always in his ways—then you shall add three more cities to these three,^*