John 8:7

(Tract. xxxiii. 5) He did not say, Stone her not, lest He should seem to speak contrary to the law. But God forbid that He should say, Stone her; for He came not to destroy that which He found, but to seek that which was lost. What then did He answer? He that is without sin among you, let him first cast a stone at her. This is the voice of justice. Let the sinner be punished, but not by sinners; the law carried into effect, but not by transgressors of the law.

What answer, then, did the Lord Jesus make? How answered the Truth? How answered Wisdom? How answered that Righteousness against which a false accusation was ready? He did not say, Let her not be stoned; lest He should seem to speak against the law. But God forbid that He should say, Let her be stoned: for He came not to lose, what He had found, but to seek what was lost. What then did He answer? See you how full it is of righteousness, how full of meekness and truth! "He that is without sin of you," saith He, "let him first cast a stone at her." O answer of Wisdom! How He sent them unto themselves! For without they stood to accuse and censure, themselves they examined not inwardly: they saw the adulteress, they looked not into themselves. Transgressors of the law, they wished the law to be fulfilled, and this by heedlessly accusing; not really fulfilling it, as if condemning adulteries by chastity. You have heard, O Jews, you have heard, O Pharisees, you have heard, O teachers of the law, the guardian of the law, but have not yet understood Him as the Lawgiver. What else does He signify to you when He writes with His finger on the ground? For the law was written with the finger of God; but written on stone because of the hard-hearted. The Lord now wrote on the ground, because He was seeking fruit. You have heard then, Let the law be fulfilled, let the adulteress be stoned. But is it by punishing her that the law is to be fulfilled by those that ought to be punished? Let each of you consider himself, let him enter into himself, ascend the judgment-seat of his own mind, place himself at the bar of his own conscience, oblige himself to confess. For he knows what he is: for "no man knoweth the things of a man, but the spirit of man which is in him." Each looking carefully into himself, finds himself a sinner. Yes, indeed. Hence, either let this woman go, or together with her receive ye the penalty of the law. Had He said, Let not the adulteress be stoned, He would be proved unjust: had He said, Let her be stoned, He would not appear gentle: let Him say what it became Him to say, both the gentle and the just, "Whoso is without sin of you, let him first cast a stone at her." This is the voice of Justice: Let her, the sinner, be punished, but not by sinners: let the law be fulfilled, but not by the transgressors of the law. This certainly is the voice of justice: by which justice, those men pierced through as if by a dart, looking into themselves and finding themselves guilty, "one after another all withdrew." The two were left alone, the wretched woman and Mercy. But the Lord, having struck them through with that dart of justice, deigned not to heed their fall, but, turning away His look from them, "again He wrote with His finger on the ground."

For he who judges not himself first, cannot know how to judge correctly in the case of another. For though He know what the offence is, from being told, yet He cannot judge of another's deserts, who supposing himself innocent, will not apply the rule of justice to himself.

So when they continued asking Him, He lifted Himself up.