28 Now Absalom had commanded his servants, saying, "Watch now, when Amnon's heart is merry with wine, and when I say to you, 'Strike Amnon!' then kill him. Do not be afraid. Have I not commanded you? Be courageous and valiant." 29 So the servants of Absalom did to Amnon as Absalom had commanded. Then all the king's sons arose, and each one got on his mule and fled.
30 And it came to pass, while they were on the way, that news came to David, saying, "Absalom has killed all the king's sons, and not one of them is left!" 31 So the king arose and tore his garments and lay on the ground, and all his servants stood by with their clothes torn. 32 Then Jonadab the son of Shimeah, David's brother, answered and said, "Let not my lord suppose they have killed all the young men, the king's sons, for only Amnon is dead. For by the command of Absalom this has been determined from the day that he forced his sister Tamar. 33 Now therefore, let not my lord the king take the thing to his heart, to think that all the king's sons are dead. For only Amnon is dead." 34 Then Absalom fled. And the young man who was keeping watch lifted his eyes and looked, and there, many people were coming from the road on the hillside behind him. 35 And Jonadab said to the king, "Look, the king's sons are coming; as your servant said, so it is." 36 So it was, as soon as he had finished speaking, that the king's sons indeed came, and they lifted up their voice and wept. Also the king and all his servants wept very bitterly.
Matthew Henry's Commentary on 2 Samuel 13:28-36
Commentary on 2 Samuel 13:21-29
(Read 2 Samuel 13:21-29)
Observe the aggravations of Absalom's sin: he would have Ammon slain, when least fit to go out of the world. He engaged his servants in the guilt. Those servants are ill-taught who obey wicked masters, against God's commands. Indulged children always prove crosses to godly parents, whose foolish love leads them to neglect their duty to God.
Commentary on 2 Samuel 13:30-39
(Read 2 Samuel 13:30-39)
Jonadab was as guilty of Ammon's death, as of his sin; such false friends do they prove, who counsel us to do wickedly. Instead of loathing Absalom as a murderer, David, after a time, longed to go forth to him. This was David's infirmity: God saw something in his heart that made a difference, else we should have thought that he, as much as Eli, honoured his sons more than God.