Now in those days the advice of Ahithophel was like the consultation of the word of God. Such was the regard that both David and Absalom had for Ahithophel’s advice.
Absalom had notice sent him speedily by some of his friends at Jerusalem that David had withdrawn, and with what a small retinue he had gone; so that the coasts were clear, Absalom might take possession of Jerusalem when he pleased. The gates were open, and there was none to oppose him.
Commenting on 2 Samuel 16:15-23
And the counsel of Ahithophel, which he had counselled in those days,.... Both in the days of David, and in the days of Absalom, before and since the rebellion: was as if a man had inquired of the oracle of God; such an opinion was entertained of it, so well satisfied were they with it, and as confident of success in taking it, as if...
And the counsel of Ahithophel, which he counselled in those days, [was] as if a man had enquired at the oracle of God: so [was] all the counsel of Ahithophel both with David and with Absalom. (l) It was so esteemed for the success of it.