Deuteronomy 19:4-6

New International Version - UK

⁴ This is the rule concerning anyone who kills a person and flees there for safety – anyone who kills a neighbour unintentionally, without malice aforethought. ⁵ For instance, a man may go into the forest with his neighbour to cut wood, and as he swings his axe to fell a tree, the head may fly off and hit his neighbour and kill him. That man may flee to one of these cities and save his life. ⁶ Otherwise, the avenger of blood might pursue him in a rage, overtake him if the distance is too great, and kill him even though he is not deserving of death, since he did it to his neighbour without malice aforethought.