Charles H. Spurgeon on Psalms 36:3

The words of his mouth are iniquity and deceit. This pair of hell dogs generally hunt together, and what one does not catch the other will; if iniquity cannot win by oppression, deceit will gain by chicanery. When the heart is so corrupt as to flatter itself, the tongue follows suit. The open sepulchre of the throat reveals the foulness of the inner nature. God fearing men make a conscience of their words, and if they sin through infirmity they do not invent excuses, or go about to boast of their wickedness: but because wicked men think little of evil and artful speeches, we may be clear that God rules not in their souls. The original by declaring that the words of the wicked are falsehood and deceit is peculiarly strong; as if they were not only false in quality, but actual falseness itself. He hath left off to be wise, and to do good. From the good way he has altogether gone aside. Men who fear God proceed from strength to strength in the right path, but godless men soon forsake what little good they once knew. How could men apostatise if they had respect unto the supreme Judge? Is it not because they grow more and more forgetful of God, that in due season they relinquish even that hypocritical reverence of him which in former days they maintained in order to flatter their souls?