To cast him down from his excellency - They are consulting to dethrone me, and use treachery and falsehood in order to bring it about: "They delight in lies."
They bless with their mouth - Probably alluding to Absalom's blandishments of the people. He flattered them in order to get the sovereign rule. Or it may refer to the people of Jerusalem, whose perfidy he saw, while they were full of professions of loyalty, etc.; but he could not trust them, and therefore retired from Jerusalem.
They only consult to cast him down from his excellency - This is the object of all their counsels and plans. They aim at one high in rank - and their purpose, their sole purpose, is to bring him down. This would apply well to the case of David in the time of the rebellion of Absalom.
They delight in lies - In false pretences; in secret plans of evil; in hypocritical assurances. This was eminently true of Absalom, who made use of these arts to seduce the people from allegiance to his father. 2 Samuel 15:1-6.
They bless with their mouth, but they curse inwardly - They profess true attachment and zeal, but they are traitors at heart. See the notes at Psalm 28:3. This, too, would apply well to the conduct of Absalom and those associated with him.