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

By the appointment of Absalom ... - Meaning that Absalom's resolution to slay Amnon had been formed at the time, and only waited an opportunity to give expression to it.

answered and said; said in answer to the report brought to the king, which threw him into such an agony:

let not my lord suppose that they have slain all the young men the king's sons; he did not believe it himself, and would not have the king entertain such a thought, and distress himself with it:

for Amnon only is dead; he is very positive, and speaks with great assurance; it looks as if he was in the secret, and knew of the plot against Amnon's life; and, if so, he must be a very wicked man, first to form a scheme whereby Amnon might come at Tamar to ravish her, and then be accessory to the murder of him, as he must, if he knew of the design against his life, and did not acquaint him and the king of it; and this seems to be confirmed by what follows:

for by the appointment of Absalom this hath been determined, from the day that he forced his sister Tamar; that is, the slaying of Amnon; the meaning is, either that Absalom had given orders to his servants to slay him, whenever they had an opportunity; or it was "in the mouth of Absalom" (p), as it may be rendered; he used to declare it to his intimate friends, that it was the purpose and resolution of his heart to kill Amnon some time or another; and this he had taken up from the time of his sister Tamar's being forced, and because of that, of which Jonadab had intelligence by some means or another; and who speaks of this rape without any seeming emotion, as if he had no concern at all in it.

(p) "in ore Absalom", V. L. Vatablus.