2 Samuel 15:12, 31

While Absalom was offering the sacrifices, he sent for Ahithophel, one of David’s counselors who lived in Giloh. Soon many others also joined Absalom, and the conspiracy gained momentum.

When someone told David that his adviser Ahithophel was now backing Absalom, David prayed, “O LORD, let Ahithophel give Absalom foolish advice!”