Numbers 35:19-21

19The blood avenger himself shall put the murderer to death; he shall put him to death when he meets him. 201If he pushed him of hatred, or threw something at him 2lying in wait and as a result he died, 21or if he struck him down with his hand in enmity, and as a result he died, the one who struck him shall surely be put to death, he is a murderer; the blood avenger shall put the murderer to death when he meets him.