Thou shalt surely kill him; not privately, which pretence would have opened the door to innumerable murders, but by procuring his death by the sentence of the magistrate; and thou shalt cast the first stone at him, as the witness was to do. See Deuteronomy 17:7 Acts 7:58.
Related Commentaries of Deuteronomy 13:9
Deuteronomy 13:9
9 But thou shalt surely kill him; thine hand shall be first upon him to put him to death, and afterwards the hand of all the people.