Numbers 35:20-23

20If any of you kills someone you hate by shoving him or by deliberately throwing something at him,

21or if you beat your enemy to death with your bare hands, you must be put to death. You are a murderer. The relative who can avenge the death must kill you when he catches up with you, because you are a murderer.

22“But suppose you accidentally kill someone who wasn’t your enemy. Maybe you shoved him or threw something at him but didn’t mean to kill him.

23Or suppose you drop a big stone, and someone is killed. However, you didn’t know the person was there, he wasn’t your enemy, and you weren’t trying to harm him.