2 Samuel 16:21-23

21And Ahithophel said unto Absalom, Go in unto thy father’s 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.

22So they spread Absalom a tent upon the top of the house; and Absalom went in unto his father’s concubines in the sight of all Israel.

23And 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.1