“And Jonadab, the son of Shimeah David's brother, answered and said, Let not my lord suppose that they have slain all the young men the king's sons; for Amnon only is dead: for by the appointment of Absalom this hath been determined from the day that he forced his sister Tamar.”
King James Version (KJV)
Matthew Henry's Concise Commentary
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.
“That thy foot may be dipped in the blood of thine enemies, and the tongue of thy dogs in the same.”