They only consult to thrust him down from his dignity,
They delight in lies,
They bless with their mouth,
But they curse inwardly. [Selah.'
He describes the kind of people that they are. Their only aim is to drag him down from his exalted position, to strip him of his authority. And in order to do so they are prepared to use lies, and false accusations. And their hypocrisy is brought out in that publicly they bless him with their mouths, while privately they curse him in their hearts. Note how their perfidy and untrustworthiness contrasts with the faithfulness and trustworthiness of God as already described. He is firm and sure, they are totally untrustworthy.
‘Selah.' Let the worshippers think of that.