And the king being sorry. His heart, as we have said, was no longer influenced by religious sentiments; but, foreseeing the detestation that will be excited by such a crime, he dreads both the loss of character and positive harm, and consequently repents of his levity. And yet he has not the courage to give a refusal to a dancing girl, lest he should incur the reproach of unsteadiness; as if it were more dishonorable to retract a rash and foolish promise than to persist in a heinous crime. With the wonted vanity of kings, he does not choose that what he has once uttered shall be recalled, and orders that the prophet shall be instantly slain. We infer that Herod was at that time supping in the castle of Macherus, where, Josephus tells us, John was imprisoned, (Ant. 18. 5:2.) On account of the oath, and of those who sat at table with him. It deserves our attention that the Evangelists state this to be the reason of his grief; and hence we infer that, though he had sworn a hundred times, yet if there had been no witness, he would not have held by his oath. No inward feelings of religion constrained Herod to do this, but the mere love of power drove him headlong; for he reckoned that he would sink in the estimation of those who were present, if he did not fulfill his engagement. Thus it frequently happens that ungodly men fail to perform their duty, because they do not look to God, but are only intent on this object, that they may not incur the reproaches of men. [1] But though Herod had kept before his eyes the sacredness of an oath alone, and not the dread of the opinion of men, he committed a more heinous offense in fulfilling a foolish promise than if he had violated his oath. First, he was deeply in fault for such haste in swearing; for the design of an oath is to confirm a promise in a doubtful matter. Next, when it appeared that he could not be relieved from his engagement without involving himself in an aggravated crime, he had no right to implicate the sacred name of God in such wickedness; for what could be more at variance with the nature of God than to lend his countenance to a shocking murder? If a private loss is at stake, let him who has made a rash oath suffer the punishment of his folly; but, when a man has taken the name of God in vain, let him beware of doubling his guilt by employing this as a pretense for committing some enormous crime. Hence it follows, that monastic vows, which are attended by open impiety, do not bind the conscience any more than the enchantments of magicians; for it is not the will of God that his sacred name shall give support to what is sinful. But this passage teaches us, that we ought to beware of making promises without consideration; and next, that lightness must not be followed by obstinacy.

Footnotes

1 - "Et ne se soucient seulement que d'eviter le blasme et la moquerie des hommes;"-- "and are only anxious to avoid the censure and ridicule of men."

For their sakes which sat with him - Probably these persons joined in with the request, and were glad of this opportunity to get this light of Israel extinguished; he being a public reprover of all their vices.

And the king was exceeding sorry,.... See Gill on Matthew 14:9.
yet for his oath's sake, and for their sakes which sat with him; as Matthew adds, "at meat", Matthew 14:9; for it seems as if supper was not over, when all this was transacting.
He would not reject her; deny her her request, or send her away without granting it which could not be without grieving her, and treating her with contempt, and defrauding her of the promise; all which ideas are expressed by some versions.

And the king was exceeding sorry--With his feelings regarding John, and the truths which so told upon his conscience from that preacher's lips, and after so often and carefully saving him from his paramour's rage, it must have been very galling to find himself at length entrapped by his own rash folly.
yet for his oath's sake--See how men of no principle, but troublesome conscience, will stick at breaking a rash oath, while yielding to the commission of the worst crimes!
and for their sakes which sat with him--under the influence of that false shame, which could not brook being thought to be troubled with religious or moral scruples. To how many has this proved a fatal snare!
he would not reject her.

Yet for his oath's sake, and for the sake of his guests - Herod's honour was like the conscience of the chief priests, Matthew 27:6. To shed innocent blood wounded neither one nor the other.