Deuteronomy 19:4-6

Leeser(i) 4 And this is the case of the man-slayer, who shall flee thither, that he may live: Whoso smiteth his neighbor without knowledge, when he hath not been an enemy to him in time past; 5 And he that goeth into the forest with his neighbor to hew wood, and his hand fetcheth a stroke with the axe to cut down the tree, and the iron slippeth from the helve, and striketh his neighbor, that he die: this one shall flee unto one of these cities, and live; 6 That the avenger of the blood pursue not the manslayer, while his heart is hot, and overtake him, because the way is long, and smite him dead; whereas he deserveth not a judgment of death, inasmuch as he was not an enemy to him in time past.