Deuteronomy 19:3-5

New International Version - UK

³ Determine the distances involved and divide into three parts the land the Lord your God is giving you as an inheritance, so that a person who kills someone may flee for refuge to one of these cities.

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.