David’s final testament to his son Solomon is more than a mere plea for vengeance; it is a profound political and moral directive designed to establish the young king’s reign upon a foundation of justice. As he prepares to pass the crown, David warns Solomon about his formidable army commander, Joab the son of Zeruiah, a man whose immense power allowed him to blur the boundaries between war and peace through acts of calculated deceit.
David's instruction reminds the young king that while he is bound to govern according to the laws of the Torah, the monarchy possesses a unique, extra-legal authority. There are times when a king must exercise this royal prerogative to execute justice upon dangerous individuals without the standard formal warnings, a measure perfectly suited for a man like Joab [מלבי״ם]. Furthermore, Solomon has firsthand experience with Joab’s treachery, having seen the commander support a rival claimant to the throne. Just as Solomon knows what Joab did to undermine his own succession, he must now fully grasp the magnitude of the offenses Joab committed against David himself [אברבנאל]. Other commentators suggest that the events are simply so well-known that they require no further elaboration [מצודת דוד, רד״ק].
The nature of Joab's personal offense against David is understood in several ways. The primary approach among commentators is that Joab’s assassination of Israel’s military leaders was a direct assault on the king. Because these commanders were acting as David’s emissaries and operating under his royal protection, their murder brought immense political and personal disgrace upon the throne. Another perspective suggests the deep personal wound was Joab’s slaying of David's son Absalom in direct defiance of the king's explicit orders, compounded by the harsh and disrespectful reprimand Joab delivered to the grieving father afterward [רלב״ג, רד״ק]. Additionally, a rich midrashic tradition explains that Joab severely damaged David’s public honor by openly displaying a secret royal letter instructing him to abandon Uriah the Hittite on the battlefield, thereby publicly shaming the king before the nation [רש״י, רד״ק, מלבי״ם, אלשיך, צאינה וראינה].
The crux of Joab’s criminality lies in his actions against the two commanders of Israel’s armies, Abner and Amasa. His behavior is characterized by three distinct evils: murdering innocent men, acting with profound deceit, and shedding blood during times of peace [אברבנאל, מלבי״ם]. Joab took the violence that is legally and morally restricted to the battlefield and dragged it into the realm of peace. He assassinated military leaders who had already forged peace treaties with David and had no intention of fighting [רש״י, מצודת דוד, ביאור שטיינזלץ]. To justify his actions, Joab falsely applied the rules of combat and self-defense to peacetime scenarios [צוארי שלל]. In the case of Abner, Joab claimed he was avenging the blood of his brother Asahel, completely ignoring the fact that Asahel was killed during an active battle where different rules of engagement apply [רד״ק].
The sheer cunning and cruelty of these murders were executed through physical tricks involving Joab's belt and shoes. When assassinating Amasa, Joab purposefully fastened his sword loosely in his belt so that it would easily fall out. As he bent down to adjust his shoe, the weapon dropped to the ground. Believing Joab was merely retrieving a fallen sword, Amasa lowered his guard, allowing Joab to strike a fatal blow [רש״י, מצודת דוד, רלב״ג]. A similarly treacherous scheme was used against Abner, centered around a legal question regarding footwear. Joab asked Abner how a woman without arms could perform the biblical ritual of removing her brother-in-law's shoe. When Abner bent down to demonstrate how she could pull the shoe off with her teeth, Joab seized the moment of vulnerability and stabbed him [רש״י, רד״ק, צאינה וראינה].
Beyond the physical weapons of his treachery, Joab's actions carried a dark metaphorical weight. He did not simply commit murder in the shadows; he openly reveled in his brutality. By smearing the blood of the fallen commanders on his belt and his shoes, Joab boasted of his supposed battlefield bravery to the army and the public [אברבנאל]. In doing so, he transformed himself into a man entirely stained, from his waist to the soles of his feet, with the blood of the innocent [ביאור שטיינזלץ].