The LORD shall cut off all flattering lips, and the tongue that speaketh proud things:
The Lord shall cut off all flattering lips - the expression of confident faith that the Lord will hear the prayer with which the psalm begins, "Help, Lord." For in order that our prayers may be heard, we must believe that God will grant them: as the Lord saith (Mark 11:24), "What things soever ye desire, when ye pray, believe that ye receive them, and ye shall have them."
And the tongue that speaketh proud things - literally, big things; i:e., the tongue that boasts of its power to deceive, as in Isaiah 28:15.