II Samuel 15:12, 31

Then Absalom sent for Ahithophel the Gilonite, David’s counselor, from his city—from Giloh—while he offered sacrifices. And the conspiracy grew strong, for the people with Absalom continually increased in number.

Then someone told David, saying, “Ahithophel is among the conspirators with Absalom.” And David said, “O LORD, I pray, turn the counsel of Ahithophel into foolishness!”