2 Samuel 16:20-23 King James Version (KJV)
20 Then said Absalom to Ahithophel, Give counsel among you what we shall do.
21 And 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.
22 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.
23 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.