Deuteronomy 19:6–12

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,^{* 10}so that the blood of an innocent person may not be shed in the land that the Lord your God is giving you as an inheritance, thereby bringing bloodguilt upon you.^*

¹¹“But if someone at enmity with another lies in wait and attacks and takes the life of that person and flees into one of these cities, ¹²then the elders of the killer’s city shall send to have the culprit taken from there and handed over to the avenger of blood to be put to death.