Numbers 35:19-23

The blood avenger himself shall put the murderer to death; he himself shall put him to death when he meets him.

Now if he pushed him in hatred, or he threw something at him with malicious intent, and as a result he died,

or if he struck him with his hand with hostility, and as a result he died, the one who struck him must be put to death; he is a murderer. The blood avenger shall put the murderer to death when he meets him.

‘But if he pushed him suddenly, without hostility, or threw any object at him without malicious intent,

or had any deadly stone, and without looking he dropped it on him so that he died, while he was not his enemy nor was he seeking to harm him,