Matthew Henry comments on the episode with Amnon and Tamar that “[David] ought to have punished [Amnon] for [violating Tamar], and have put him to open shame; both as a father and as a king he had power to do it.” Since the law of God demands that His people be impartial in administering justice (Ex. 23:2–3, 6, 8), David was obligated to make sure that even the royal prince not get away with his crimes. Yet, David did nothing except get angry (2 Sam. 13:1–22). This negligence with respect to his own family, as we will see, would characterize much of David’s life after his sin with Bathsheba. His moral senses were dulled, and he began to fail in discerning the affairs in his own household and in dealing properly with his children.
David’s anger at Amnon did not bear fruit in any action to secure justice for Tamar. Amnon and Tamar’s brother Absalom, on the other hand, refused to let Amnon get away with what he had done. He took matters into his own hand and ended up crossing the line from justice into pure revenge. Earlier, Amnon was able to deceive David regarding Amnon’s true intent for Tamar, convincing him to send Tamar to Amnon’s chamber (vv. 1–22). Two years later, Absalom fooled David regarding what was in store for Amnon, persuading David to send Amnon right into an ambush (vv. 23–29). The lack of wisdom on David’s part stands out, as well as Absalom’s refusal to go through the proper channels to have Amnon dealt with. Absalom bided his time, saying nothing of the matter to Amnon for years until he could find the right opportunity to kill his brother (v. 22).
Chaos had descended on David’s house, and that chaos would soon spread throughout the land in fulfillment of Nathan’s prophecy in 2 Samuel 12:10–11. “By justice a king builds up the land” (Prov. 29:4), so David’s failure to pursue justice in the matter of Amnon could not help but to tear down the land. Fearing for his life, Absalom fled to his grandfather Talmai, king of Geshur, a small kingdom west of the territory belonging to Manasseh that Israel had not conquered as they were supposed to (2 Sam. 13:30–37; see 3:3). There he would stay for three years while David mourned the death of Amnon, and though Absalom would return to David, their relationship would never be the same (13:38–39). Soon Absalom would lead a revolt and David would almost lose his kingdom—all because justice for Tamar was deferred.