Matthew Poole and continuators on 2 Samuel 16:21

21 And Ahitophel said unto Absalom, Go in unto thy fathers concubines , which he hath left to keep the house, and all Israel shall hear that thou art abhorred of thy father , then shall the hands of all that are with thee be strong e.

This Counsel he gave, partly to Revenge the Injury done to Bathsheba, who was the Daughter of Eliam, 2 Sam. 11. 3. who was the Son of Ahitophel, Chap. 23. 34. and principally, for his own, and the Peoples safety, that the Breach between David and Absalom might be made wide, and irreparable by so Vile an Action; which must needs provoke David in the highest Degree, both for the Sin, and shame of it; as the like Action had done Iacob, Gen. 49. 3, 4. and cut off all hopes of Reconciliation, which otherwise might have been expected by some Treaty between Absalom and his render-hearted Father; in which Case his Followers, and especially Ahitophel himself, had been left to David's Mercy.

And therefore obliged by thy own Interest to Prosecute the War with all possible Vigor, and to abandon all thoughts of Peace: as knowing that his Father, though he might dissemble, yet would never forgive so foul and scandalous a Crime. Yea, they will Fight with greater Courage and Resolution, when they are freed from the fear of thy Reconciliation, which otherwise would make their Hearts saint, and Hands slack in thy Cause. But by this we may see the Character of Absalom's Party, and how abominably wicked they were, whom such a loathsome and Scandalous Action tied the faster to him, whom for that very reason they should have deserted and abhorred. And we may further learn, how corrupt and filthy the Body of the People was, and how ripe for that severe judgment which is now hastening to them.

Marginal references: Heb. stinkest with thy father.