Psalm 36:3

The words of his mouth [are] iniquity and deceit
Not only sinful, but sin itself; his mouth is full of cursing and bitterness, of filthy and unchaste words, of corrupt communication, lying, deceit, and flattery; out of the abundance of the wickedness of his heart his mouth speaketh; and which shows the badness of it, and proves all that is said before of him;

he hath left off to be wise, [and] to do good;
by which the psalmist seems to intend one that had been a professor of religion, who, besides the light of nature he had acted contrary to, had had the advantage of a divine revelation, and had been enlightened into the knowledge of divine things, and had done many things externally good, particularly acts of beneficence; but now had dropped his profession of religion, denied the truths he had been enlightened into, and ceased from doing good; otherwise a natural man understandeth not; and, though he is wise to do evil, to do good he has no knowledge.