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. I may not tarry thus with thee - He had nothing to say in vindication of the purpose he had formed.
Thrust them through the heart of Absalom - He was determined to make sure work, and therefore he pierced his heart.
Joab should have obeyed the king's commandment: and yet the safety of the state required the sacrifice of Absalom. But independently of this, his life was quadruply forfeited to the law: -
1. In having murdered his brother Amnon.
2. In having excited an insurrection in the state.
3. In having taken up arms against his own father, Deuteronomy 21:18, Deuteronomy 21:21.
4. In having lain with his father's concubines, Leviticus 18:29.
Long ago he should have died by the hand of justice; and now all his crimes are visited on him in his last act of rebellion. Yet, in the present circumstances, Joab's act was base and disloyal, and a cowardly murder.