And the king was sorry - There might have been several reasons for this.
1. Herod had a high respect for John, and feared him. He knew that he was a holy man, and had "observed him," Mark 6:20. In the margin (Mark) this is "kept him," or "saved him." In fact he had interposed and saved John from being put to death by Herodias, who had had a quarrel with John, and would have killed him but for Herod, Mark 6:19. Herod, though a bad man, had a respect and veneration for John as a holy and just man, as wicked people often will have.
2. John was in high repute among the people, and Herod might have been afraid that his murder might excite commotion.
3. Herod, though a wicked man, does not appear to have been insensible to some of the common principles of human nature. Here was a great and most manifest crime proposed - no less than the murder of an acknowledged prophet of the Lord. It was deliberate. It was to gratify the malice of a wicked woman. It was the price of a few moments' entertainment. His conscience, though in feeble and dying accents, checked him. He would have preferred a request not so manifestly wicked, and that would not have involved him in so much difficulty.
For the oath's sake - Herod felt that he was bound by this oath; but he was not. The oath should not have been taken: but, being taken, he could not be bound by it. No oath could justify a man in committing murder. The true principle is, that Herod was bound by a prior obligation - by the law of God - not to commit murder; and no act of his, be it an oath or anything else, could free him from that obligation.
And them which sat with him at meat - This was the strongest reason why Herod murdered John. He had not firmness enough to obey the law of God and to follow the dictates of conscience against the opinions of wicked people. He was afraid of the charge of cowardice and want of spirit; afraid of ridicule and the contempt of the wicked. This is the principle of the laws of honor; this the foundation of dwelling. It is not so much for his own sake that one man murders another in a duel, for the offence is often a mere trifle - it is a word, or look, that never would injure him. It is because the "men of honor," as they call themselves, his companions, would consider him a coward and would laugh at him. Those companions may be unprincipled contemners of the laws of God and man; and yet the duellist, against his own conscience, against the laws of God, against the good opinion of the virtuous part of the world, and against the laws of his country, seeks by deadly aim to murder another merely to gratify his dissolute companions. And this is the law of honor! This is the secret of duelling! This the source of that remorse that settles in awful blackness, and that thunders damnation around the duellist in his dying hours! It should be added, this is the course of all youthful guilt. Young men are led along by others. They have not firmness enough to follow the teachings of a father and of the law of God. They are afraid of being called mean and cowardly by the wicked; and they often sink low in vice and crime, never to rise again.
At meat - That is, at supper. The word "meat," at the time the Bible was translated, meant provisions of all kinds. It is now restricted to flesh, and does not convey a full idea of the original.

The king was sorry - He knew John to be a righteous man, and at first did many things gladly which John told him it was his duty to perform: Mark 6:20.
Nevertheless, for the oath's sake - The Oaths, ορκους - he had probably sworn again and again - one sin begets many.
And them which sat with him at meat - Who were probably such as himself, and would have considered it a breach of honor if he had not fulfilled his sworn promise: he therefore commanded it to be given!

And the king was sorry,.... As he might be upon many accounts; partly on account of John, whom, notwithstanding his freedom in reproving him, he had a respect; and partly on his own account, his conscience dictating to him that it was an evil action, and would leave a brand of perpetual infamy upon him; as also on account of the people, who were so much affected to John, lest they should make an insurrection, and rebel against him; and likewise, because it was reckoned an ill omen with the Romans, to take away life on that day they received their own; and therefore carefully abstained, on such days, from executions.
Nevertheless for his oath's sake; that he might not be guilty of perjury, chose rather to commit murder; though it would have been no iniquity in him, to have acted contrary to such a rash promise, and wicked oath; which would have been better to have been broke, than kept;
and them which sat with him at meat; lest he should be thought by them fickle and inconstant, and not a man of his word, and who had no regard to an oath: or it may be, they, either to curry favour with Herodias, or out of ill will they might bear to John; or in great respect to the damsel, who had so well pleased them with her dancing; instead of dissuading him from it, pressed him much to perform his promise: and therefore,
he commanded it to be given her; in the form and manner she requested it. Some have thought, that the whole of this affair was a concerted scheme; and that Herod himself was in it, though he pretended to be sorry and uneasy, having fixed on this season as a convenient time for it; and chose to have it done in this way, and in so public a manner, to lessen the odium of it; or otherwise, it is not easy to account for his extravagant promise, and his punctual performance of it.

The king was sorry. The Greek word thus translated is very strong, and denotes a very great grief, and sorrow.
For the oath's sake, and them which sat with him. It was not so much his regard for the oath which he had taken, but his shrinking from the taunt of the guests, if they should see him draw back from his plighted word.

And the king was sorry - Knowing that John was a good man. Yet for the oath's sake - So he murdered an innocent man from mere tenderness of conscience.