Deuteronomy 19:5

for instance whosoever shall go with his neighbour into the forest to collect wood, and the hand of him who is cutting the wood with an axe being drawn back, the iron shall slip from the helve, and accidentally fall on his neighbour, and he die; such a one shall flee with speed to one of the cities, and live.

And whosoever shall enter with his neighbour into the thicket, to gather wood, if the hand of him that cuts wood with the axe should be violently shaken, and the axe head falling off from the handle should light on his neighbour, and he should die, he shall flee to one of these cities, and live.