Charles Ellicott Commentary 2 Samuel 13:32

"And Jonadab, the son of Shimeah, David`s brother, answered and said, Let not my lord suppose that they have killed 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." — 2 Samuel 13:32 (ASV)

Jonadab. —The same subtle counsellor who had led Amnon into his sin, now at once divined how the case really stood and reassured the king.

By the appointment of Absalom this has been determined. —Literally, upon Absalom’s mouth it has been set, an expression which has given rise to much variety of interpretation. The Authorised Version expresses the sense accurately.