Psalms 36:3

“The words of his mouth [are] iniquity and deceit, etc.] 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…”

“The words of his mouth are iniquity and deceit - Are false and wicked. See the notes at Psalms 12:2. It is words do not fairly represent or express what is in his heart. He hath left off to be wise - To act wisely; to do right. And to do good - To act benevolently and kindly. This would seem to imply that there had been a change in his conduct, or that he was not what he once professed to be, and appeared to be. This language would be applicable to the change in the conduct of Saul toward David after he became envious and jealous of him 1 Samuel 18:0; and it is possible, as Amyraldus supposed, that this may have had particular reference to him. But such instances of a change, of feeling and…”

“Left off - Once he had some degrees of wisdom, but now he is become an open apostate. Psalms 36:4”

“The words: Psa 5:9, Psa 12:2, Psa 12:3, Psa 55:21, Psa 58:3, Psa 140:3; Sa1 18:21, Sa1 19:6, Sa1 19:7, Sa1 26:21; Mat 22:15-18, Mat 22:35 he hath: Psa 125:5; Sa1 11:6-13, Sa1 13:13, Sa1 13:14, Sa1 15:26, Sa1 16:14; Zep 1:6; Heb 10:39; Jo1 2:19 Psalms 36:4”