2 Samuel 16:20-23

Then said Absalom to Ahithophel, Give your counsel what we shall do. And Ahithophel said unto Absalom, Go in unto thy father’s concubines, that he hath left to keep the house; and all Israel will hear that thou art abhorred of thy father: then will the hands of all that are with thee be strong. So 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. And the counsel of Ahithophel, which he gave in those days, was as if a man inquired at the oracle of God: so was all the counsel of Ahithophel both with David and with Absalom.