Deuteronomy 19:4-10

“This is the provision for the manslayer, who by fleeing there may save his life. If anyone kills his neighbor unintentionally without having hated him in the past— as when someone goes into the forest with his neighbor to cut wood, and his hand swings the axe to cut down a tree, and the head slips from the handle and strikes his neighbor so that he dies—he may flee to one of these cities and live, lest the avenger of blood in hot anger pursue the manslayer and overtake him, because the way is long, and strike him fatally, though the man did not deserve to die, since he had not hated his neighbor in the past. Therefore I command you, You shall set apart three cities. And if the LORD your God enlarges your territory, as he has sworn to your fathers, and gives you all the land that he promised to give to your fathers— provided you are careful to keep all this commandment, which I command you today, by loving the LORD your God and by walking ever in his ways—then you shall add three other cities to these three, lest innocent blood be shed in your land that the LORD your God is giving you for an inheritance, and so the guilt of bloodshed be upon you.