Deuteronomy 19:5-7

Revised Standard Version Catholic Edition

⁵ as when a man 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 save his life; ⁶ lest the avenger of blood in hot anger pursue the manslayer and overtake him, because the way is long, and wound him mortally, though the man did not deserve to die, since he was not at enmity with his neighbor in time past. ⁷ Therefore I command you, You shall set apart three cities.