The wicked’s speech is full of arrogance; that is, their words bear no reverence for God or concern for others (see Psalm 10:3–6), and declare their great plans for bringing trouble to the psalmist. It is a rather treacherous thing, pointing to their complete untrustworthiness. The arrogant, even when speaking properly, has his heart full of his own ego; and at any time his words may become a torrent of curses in order to accomplish his will.
1
10 They close their hearts to pity; with their mouths they speak arrogantly.