John 8:5-6

Now Moses commanded that such should be stoned If they spoke accurately, this must have been a woman who, having been betrothed to a husband, had been guilty of this crime before the marriage was completed, for such only Moses commanded to be stoned. He commanded, indeed, that other adulteresses should be put to death; but the manner of death was not specified. It may be inferred, however, from Ezekiel 16:38, that though the law of Moses did not expressly enjoin it, the Jews considered stoning as being the proper punishment of all kinds of adultery, for there the prophet represents God as saying, concerning Jerusalem, I will judge thee as women that break wedlock are judged; they shall stone thee with stones. Add to this, we find Philo and the ancient Christian fathers using the phrases, “those that were stoned,” and “those that were punished for adultery,” as synonymous terms. This they said, tempting him, that they might accuse him Either of usurping the office of a judge, if he condemned her, or of being an enemy to the law, if he acquitted her. But Jesus stooped down, and wrote on the ground Perhaps there were in this woman's case some circumstances tending to alleviate her guilt, such as her past innocence, known to Jesus, her present repentance, which he could easily discern, and the strength of the temptations by which she had been hurried into sin. There may have been something likewise in her accusers' characters well known to him, which made it proper for them to desist from the prosecution. Also, Jesus might now, as on other occasions, decline assuming the character and office of a civil magistrate. Lastly, the persons who demanded his opinion were by no means the judges to whom the execution of the law was committed; but Pharisees, who at the bottom were gross hypocrites, notwithstanding they professed the greatest concern for the honour of the divine law. Whatever was the reason, Jesus did not encourage this prosecution; but with his finger wrote on the ground, as though he heard them not Or had not been attending to what they said: for, to write on the ground is the action of one who, being wholly wrapped up in his own thoughts, does not take notice of any thing that passes without.