2 Samuel 15:32-37

It happened when David came to the summit [of the Mount of Olives], where he worshiped God, behold, Hushai the Archite came to meet him with his tunic torn and dust on his head [as if in mourning]. David said to him, “If you go on with me, you will be a burden to me. But if you return to the city, and say to Absalom, ‘I will be your servant, O king; as I have been your father’s servant in the past, so I will be your servant now;’ then you can thwart (make useless) the advice of Ahithophel for me. Are not Zadok and Abiathar the priests with you there? So it shall be that every word you hear from the king’s palace, you shall report it to them. Their two sons are there with them, Ahimaaz, Zadok’s son and Jonathan, Abiathar’s son; and by them you shall send to me everything that you hear.” So Hushai, David’s friend, returned to the city, and [at about the same time] Absalom came into Jerusalem.