2 Samuel 16:21-23

21And Ahithophel said to Absalom, “Go in to your father’s concubines, whom he has left to keep the house; and all Israel will hear that you are abhorred by your father. Then the hands of all who are with you will be strong.”

22So they pitched a tent for Absalom on the top of the house, and Absalom went in to his father’s concubines in the sight of all Israel.

23Now the advice of Ahithophel, which he gave in those days, was as if one had inquired at the oracle of God. So was all the advice of Ahithophel both with David and with Absalom.