2 Samuel 16:20 (KJV)

And Absalom, and all the people the men of Israel, came to Jerusalem, and Ahithophel with him.

And it came to pass, when Hushai the Archite, David's friend, was come unto Absalom, that Hushai said unto Absalom, God save the king, God save the king.

And Absalom said to Hushai, Is this thy kindness to thy friend? why wentest thou not with thy friend?

And Hushai said unto Absalom, Nay; but whom the LORD, and this people, and all the men of Israel, choose, his will I be, and with him will I abide.

And again, whom should I serve? should I not serve in the presence of his son? as I have served in thy father's presence, so will I be in thy presence.

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.

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 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.