Augustine of Hippo

And now observe wherein the Lord's gentleness was tempted by His enemies. "And the scribes and Pharisees brought to Him a woman just taken in adultery: and they set her in the midst, and said to Him, Master, this woman has just been taken in adultery. Now Moses in the law commanded us, that such should be stoned: but what sayest thou? But this they said, tempting Him, that they might accuse Him." Why accuse Him? Had they detected Himself in any misdeed; or was that woman said to have been concerned with Him in any manner? …

Tractates on John 33 ↗

Bede

If he determined that she was to be stoned, they would scoff at him inasmuch as he had forgotten the mercy that he was always teaching. If he prohibited the stoning, they would gnash their teeth at him, and, as they saw it, rightly condemn him as a doer of wicked deeds contrary to the law. But it was beyond the ability of earthly stupidity to find out what he would say and from heavenly wisdom to fail [to know] what he would answer. …

Homilies on the Gospels 1.25 ↗

Thomas Aquinas

Then (v 3), our Lord wards off his opponents. First, we see him tested, so that he can then be accused; and secondly, he checks his accusers (v 6b). As to the first, the Evangelist does three things: first, he mentions the occasion for the test; secondly, he describes the test itself (v 4); and thirdly, the purpose of those who were testing our Lord. The occasion for the test is a woman's adultery. And so first, her accusers detail the crime; and also exhibit the sinner. …

Commentary on John ↗