Moreover Ahithophel said unto Absalom, Let me now choose out twelve thousand men, and I will arise and pursue after David this night:

And Achitophel said to Absalom: I will choose me twelve thousand men, and I will arise and pursue after David this night.

Then Ahithophel said to Absalom, Let me take out twelve thousand men and this very night I will go after David:

This night - The night of the day on which David fled, and Absalom entered into Jerusalem. Ahithophel's idea was to fall upon David by surprise, and in the first confusion of the surprised army to seize and kill David only.

Let me now choose out twelve thousand men - Had this counsel been followed, David and his little troop would soon have been destroyed; nothing but the miraculous interposition of God could have saved them. Twelve thousand chosen troops coming against him, in his totally unprepared state, would have soon settled the business of the kingdom. Ahithophel well saw that, this advice neglected, all was lost.

Moreover Ahithophel said unto Absalom, (a) Let me now choose out twelve thousand men, and I will arise and pursue after David this night:
(a) The wicked are so greedy to execute their malice, that they leave no opportunity that may further the same.

Moreover, Ahithophel said unto Absalom,.... Either at the same time, or quickly after he had given the foregoing advice:
let me now choose out twelve thousand men: out of those that were with Absalom, which shows their number to be large; and twelve thousand are pitched upon with respect to the twelve tribes of Israel, a thousand from every tribe; Josephus has only ten thousand:
and I will arise and pursue after David this night; he took upon him to be general of the army, as well as a counsellor; or this he said to show how confident he was of the success of his counsel, that if Absalom, or any other, should decline the conduct of the army upon it, as a hazardous attempt, he would undertake it himself; or rather it may be, he was not willing that Absalom should go out in person with the army, not so much for his own safety, as lest through his affection for the king he should spare him, when he fell into his hands, or they two should be reconciled; he proposed to do it that night, partly for expedition, no time being to be lost, and partly for the greater surprise of David and his men.

Here was a wonderful effect of Divine Providence blinding Absalom's mind and influencing his heart, that he could not rest in Ahithophel's counsel, and that he should desire Hushai's advice. But there is no contending with that God who can arm a man against himself, and destroy him by his own mistakes and passions. Ahithophel's former counsel was followed, for God intended to correct David; but his latter counsel was not followed, for God meant not to destroy him. He can overrule all counsels. Whatever wisdom or help any man employs or affords, the success is from God alone, who will not let his people perish.

AHITHOPHEL'S COUNSEL OVERTHROWN BY HUSHAI. (2-Samuel 17:1-14)
Moreover Ahithophel said unto Absalom--The recommendation to take prompt and decisive measures before the royalist forces could be collected and arranged, evinced the deep political sagacity of this councillor. The adoption of his advice would have extinguished the cause of David; and it affords a dreadful proof of the extremities to which the heartless prince was, to secure his ambitious objects, prepared to go, that the parricidal counsel "pleased Absalom well, and all the elders of Israel." It was happily overruled, however, by the address of Hushai, who saw the imminent danger to which it would expose the king and the royal cause. He dwelt upon the warlike character and military experience of the old king--represented him and his adherents as mighty men, who would fight with desperation; and who, most probably, secure in some stronghold, would be beyond reach, while the smallest loss of Absalom's men at the outset might be fatal to the success of the conspiracy. But his dexterity was chiefly displayed in that part of his counsel which recommended a general levy throughout the country; and that Absalom should take command of it in person--thereby flattering at once the pride and ambition of the usurper. The bait was caught by the vainglorious and wicked prince.

Ahithophel's advice frustrated by Hushai. - 2-Samuel 17:1-3. Ahithophel said still further to Absalom, "I will choose out twelve thousand men, and arise, and pursue after David this night; and fall upon him when he is exhausted and weak, and fill him with alarm: so shall all the people that are with him flee; and I will smite the king alone (when he is alone), and will bring back all the people to thee." הלּילה, the night, is the night following the day of David's flight and Absalom's entrance into Jerusalem, as we may see very clearly from 2-Samuel 17:16. This advice was sagaciously conceived; for if David had been attacked that night by a powerful army, he might possibly have been defeated. אשׁיבה, to bring back, may be explained on the supposition that Ahithophel regarded Absalom as king, and those who had fled with David as rebels, who were to be brought back under Absalom's sceptre. The following words, וגו הכּל כּשׁוּב, "as the return of the whole (the whole nation) is the man," i.e., the return of all is dependent upon David, for whom thou liest in wait, are somewhat difficult, though the meaning of Ahithophel is evident enough from what precedes: viz., if he is beaten, they will all come over to thee; "the whole nation will be at peace" (שׁלוּם is used adverbially).
(Note: Consequently no conjectures are needed as to the rendering of the words in the lxx, viz., καθὼς (al. ὅν τρόπον) ἐπιστρέρει ἡ νύμφη πρὸς τὸν ἄνδρα αὐτῆς· πλὴν ψυχὴν ἀνδρὸς ἑνὸς σὺ ζητεῖς, such as Ewald, Thenius, and Bttcher have attempted. For it is very obvious that ἡ νύμφη πρὸς τὸν ἄνδρα αὐτῆς owes its origin simply to a false reading of האישׁ הכּל as אישׁ הכּלּה, and that πλὴν ψυχὴν ἀνδρὸς ἑνός has been interpolated by way of explanation from nothing but conjecture. No other of the ancient versions contains the slightest trace of a different reading from that given in the text.)