2 Samuel 18:12 (KJV)

And a certain man saw it, and told Joab, and said, Behold, I saw Absalom hanged in an oak.

And Joab said unto the man that told him, And, behold, thou sawest him, and why didst thou not smite him there to the ground? and I would have given thee ten shekels of silver, and a girdle.

And the man said unto Joab, Though I should receive a thousand shekels of silver in mine hand, yet would I not put forth mine hand against the king’s son: for in our hearing the king charged thee and Abishai and Ittai, saying, Beware that none touch the young man Absalom.

Otherwise I should have wrought falsehood against mine own life: for there is no matter hid from the king, and thou thyself wouldest have set thyself against me.

Then said Joab, I may not tarry thus with thee. And he took three darts in his hand, and thrust them through the heart of Absalom, while he was yet alive in the midst of the oak.