John 8:7 - Matthew Poole's English Annotations on the Holy Bible

They will not let our Saviour alone, but importune him for an answer. He saith, He that is without sin, let him first cast a stone at her. The law of God was, Deuteronomy 17:7, that in the execution of malefactors, The hands of the witnesses shall be first upon him to put him to death. In reason those who are zealous for the punishment of others, should neither be guilty of the same, nor of greater crimes, themselves. By this saying of our Saviour, we must not understand it the will of God, that those who are magistrates, and employed in executing the Lord's vengeance on malefactors, should themselves be free from all guilt, for then no justice should be done. The vengeance is God s, not theirs; it is the law of God which they execute. He only by this minds them of that compassion which ought to be found in persons prosecuting others justly, that they may execute judgment with compassion and tenderness, and such moderation as the law will allow them, considering that they are not free from guilt, but as obnoxious to the justice of God for other sins, as those poor creatures whom God hath suffered to fall into sins punishable by human judges.