11 Joab said to the man who told him, "If you saw him, why didn't you kill him then and there? I'd have rewarded you with ten pieces of silver and a fancy belt." 12 The man told Joab, "Even if I'd had a chance at a thousand pieces of silver, I wouldn't have laid a hand on the king's son. We all heard the king command you and Abishai and Ittai, 'For my sake, protect the young man Absalom.' 13 Why, I'd be risking my life, for nothing is hidden from the king. And you would have just stood there!" 14 Joab said, "I can't waste my time with you." He then grabbed three knives and stabbed Absalom in the heart while he was still alive in the tree; 15 by then Absalom was surrounded by ten of Joab's armor bearers; they hacked away at him and killed him.
Matthew Henry's Commentary on 2 Samuel 18:11-15
Commentary on 2 Samuel 18:9-18
(Read 2 Samuel 18:9-18)
Let young people look upon Absalom, hanging on a tree, accursed, forsaken of heaven and earth; there let them read the Lord's abhorrence of rebellion against parents. Nothing can preserve men from misery and contempt, but heavenly wisdom and the grace of God.