Numbers 35:19-21

19The blood avenger himself shall put the murderer to death; he himself shall put him to death when he meets him. 20Now 1if he pushed him in hatred, or he threw something at him 23with malicious intent, and as a result he died, 21or 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.