(1) Pursue after David this night.—Ahithophel saw clearly that Absalom’s success depended on striking an immediate blow. He felt confident, and perhaps with reason, that David in his distress and weariness was in no condition to resist a sudden onset. That he was wise in his counsel is made plain by the opposition of Hushai and the anxiety to send tidings to David with all speed. “This night” is generally taken to mean the night of the day on which David left Jerusalem; but from 2Samuel 17:16 and 2Samuel 15:28 it appears that he was already encamped by the fords of the Jordan, a greater distance than he could have accomplished in one day’s march.

2Sa 17:1-14. Ahithophel's Counsel Overthrown by Hushai.

1-11. 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.Hushai, David’s friend, being, by David’s order, gone over to Absalom, by God’s appointment overthroweth Ahithophel’s counsel, 2 Samuel 17:1-14. Hushai certifieth David thereof, and adviseth him forthwith to march on, 2 Samuel 17:15-21. David passeth over Jordan, 2 Samuel 17:22. Ahithophel hangeth himself, 2 Samuel 17:23. David cometh to Mahanaim: Absalom passeth over Jordan, making Amasa the captain of his host, 2 Samuel 17:21-26. David is there furnished with provisions by his friends, 2 Samuel 17:27-29.

I am so well assured of the goodness of this counsel, that I will venture my own person and life in execution of it.

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.

(a) The wicked are so greedy to execute their malice, that they leave no opportunity that may further the same.