Numbers 35:20-21

If in his hate he put a sword through him, or waiting secretly for him sent a spear or stone at him, causing his death; Or in hate gave him blows with his hand, causing death; he who gave the death-blow is to be put to death; he is a taker of life: he whose right it is to give punishment for blood may put to death the taker of life when he comes face to face with him.