2 Samuel 15:30-31

30David walked up the road to the Mount of Olives, weeping as he went. His head was covered and his feet were bare as a sign of mourning. And the people who were with him covered their heads and wept as they climbed the hill.

31When someone told David that his adviser Ahithophel was now backing Absalom, David prayed, “O Lord, let Ahithophel give Absalom foolish advice!”