They say unto him, Master, this woman was taken in adultery, in the very act.

Jamieson-Fausset-Brown Bible Commentary

4, 5. woman . in adultery . Moses . commanded . should be stoned-simply put to death (De 22:22), but in aggravated cases, at least in later times, this was probably by stoning (Eze 16:40).

but what sayest thou-hoping, whatever He might answer, to put Him in the wrong:-if He said, Stone her, that would seem a stepping out of His province; if He forbade it, that would hold Him up as a relaxer of the public morals. But these cunning hypocrites were overmatched.

Matthew Henry's Concise Commentary

8:1-11 Christ neither found fault with the law, nor excused the prisoner's guilt; nor did he countenance the pretended zeal of the Pharisees. Those are self-condemned who judge others, and yet do the same thing. All who are any way called to blame the faults of others, are especially concerned to look to themselves, and keep themselves pure. In this matter Christ attended to the great work about which he came into the world, that was, to bring sinners to repentance; not to destroy, but to save. He aimed to bring, not only the accused to repentance, by showing her his mercy, but the prosecutors also, by showing them their sins; they thought to insnare him, he sought to convince and convert them. He declined to meddle with the magistrate's office. Many crimes merit far more severe punishment than they meet with; but we should not leave our own work, to take that upon ourselves to which we are not called. When Christ sent her away, it was with this caution, Go, and sin no more. Those who help to save the life of a criminal, should help to save the soul with the same caution. Those are truly happy, whom Christ does not condemn. Christ's favour to us in the forgiveness of past sins should prevail with us, Go then, and sin no more.