Ahitophel

"And Ahithophel said to Absalom, “Go in to your father’s concubines, whom he has left to keep the house; and all Israel will hear that you are abhorred by your father. Then the hands of all who are with you will be strong.”"

"Moreover Ahithophel said to Absalom, “Now let me choose twelve thousand men, and I will arise and pursue David tonight. I will come upon him while he is weary and weak, and make him afraid. And all the people who are with him will flee, and I will strike only the king. Then I will bring back all the people to you. When all return except the man whom you seek, all the people will be at peace.”"

"Now the advice of Ahithophel, which he gave in those days, was as if one had inquired at the oracle of God. So was all the advice of Ahithophel both with David and with Absalom."