(20) And now, behold, I know well that thou shalt surely be king.—Clericus (in Lange) says: “From this great magnanimity of David, Saul concluded that a man who was much superior in soul to kings could not but reign.” This is a good comment, and doubtless expresses something of what was in Saul’s mind on this occasion; but more must have been behind to have induced the king to make such a speech to David. Never had he for one moment forgotten his old friend’s words—the words of Samuel, whom he too well knew was the prophet of the Most High—when he with all solemnity announced to him, as a message from heaven, that the Lord had rent the kingdom from him, and had given it to a neighbour that was better than he (1Samuel 15:21). Since that awful denunciation, the unhappy Saul was only too sensible that the blessing of Jehovah of Hosts no longer rested on his head, no longer blessed his going out and coming in, while the strange, bright career of the son of Jesse seemed to point him out as the neighbour on whom the choice of God had fallen. Rumours, too, of a mysterious anointing must have long ere this reached Saul; this, joined to the passionate advocacy of Jonathan, and the quiet, steady friendship of Samuel, no doubt convinced King Saul that in the son of Jesse he saw Israel’s future monarch. Strong, therefore, in this conviction, and for the time humiliated and grieved at the sorry part he had been playing in this restless persecution of one destined to fill so great a position, the king positively entreats the outlaw to swear to him the strange promise contained in the next (21st) verse.

1 Samuel 24:20-21. And now I know well that thou shalt surely be king — These wonderful dispensations of Divine Providence over David, and David’s no less wonderful virtue, at last convinced Saul that God designed him to be the king of his people, and that none could hinder his establishment. That thou wilt not destroy my name, &c. — As it was usual for kings to do in those days, generally destroying the families of those to whose thrones they were advanced.

24:16-22 Saul speaks as quite overcome with David's kindness. Many mourn for their sins, who do not truly repent of them; weep bitterly for them, yet continue in love and in league with them. Now God made good to David that word on which he had caused him to hope, that he would bring forth his righteousness as the light, Ps 37:6. Those who take care to keep a good conscience, may leave it to God to secure them the credit of it. Sooner or later, God will force even those who are of the synagogue of Satan to know and to own those whom he has loved. They parted in peace. Saul went home convinced, but not converted; ashamed of his envy to David, yet retaining in his breast that root of bitterness; vexed that when at last he had found David, he could not find in his heart to destroy him, as he had designed. Malice often seems dead when it is only asleep, and will revive with double force. Yet, whether the Lord bind men's hands, or affect their hearts, so that they do not hurt us, the deliverance is equally from him; it is an evidence of his love, and an earnest of our salvation, and should make us thankful.After whom ... - i. e., was it consistent with the dignity of the king of Israel to lead armies in pursuit of a weak and helpless individual like David? 1Sa 24:8-15. He Urges Thereby His Innocency.

8-15. David also arose … and went out of the cave, and cried after Saul—The closeness of the precipitous cliffs, though divided by deep wadies, and the transparent purity of the air enable a person standing on one rock to hear distinctly the words uttered by a speaker standing on another (Jud 9:7). The expostulation of David, followed by the visible tokens he furnished of his cherishing no evil design against either the person or the government of the king, even when he had the monarch in his power, smote the heart of Saul in a moment and disarmed him of his fell purpose of revenge. He owned the justice of what David said, acknowledged his own guilt, and begged kindness to his house. He seems to have been naturally susceptible of strong, and, as in this instance, of good and grateful impressions. The improvement of his temper, indeed, was but transient—his language that of a man overwhelmed by the force of impetuous emotions and constrained to admire the conduct, and esteem the character, of one whom he hated and dreaded. But God overruled it for ensuring the present escape of David. Consider his language and behavior. This language—"a dead dog," "a flea," terms by which, like Eastern people, he strongly expressed a sense of his lowliness and the entire committal of his cause to Him who alone is the judge of human actions, and to whom vengeance belongs, his steady repulse of the vindictive counsels of his followers; the relentings of heart which he felt even for the apparent indignity he had done to the person of the Lord's anointed; and the respectful homage he paid the jealous tyrant who had set a price on his head—evince the magnanimity of a great and good man, and strikingly illustrate the spirit and energy of his prayer "when he was in the cave" (Ps 142:1).

I know well, or, am convinced, not only by the fame of Samuel’s anointing thee, but by God’s singular providence watching over thee, and by that good Spirit and those great and princely virtues wherewith God hath endowed thee.

And now, behold, I know well that thou shalt surely be king,.... Not merely by the common report, that he was anointed by Samuel, to which yet he might give credit; but by the providence of God prospering and preserving him, and by his princely spirit and behaviour, and by calling to mind what Samuel had said to him, that his kingdom should be given to a neighbour of his better than he, and so David was by his own confession, 1 Samuel 24:17; and the cutting off the skirt of his garment might put him in remembrance of the rending of the skirt of Samuel's mantle, upon which he told Saul his kingdom should be rent from him; though some think that was Saul's skirt, and so now he knew thereby, when David cut off his skirt, that the kingdom would be his; and it is a tradition of the Jews (f), that Samuel said to him at that time, that he that cut off the skirt of his garment should reign after him:

and that the kingdom of Israel shall be established in thine hand; and not be rent from him; and yet notwithstanding after this he sought to destroy him.

(f) Midrash Tillim apud Abarbinel. in loc.

And now, behold, I {g} know well that thou shalt surely be king, and that the kingdom of Israel shall be established in thine hand.

(g) Though this tyrant saw and confessed the favour of God toward David, yet he did not cease to persecute him against his own conscience.