Psalm 36 begins with an interesting phrase in the title and first verse which could be read in one of three ways, as demonstrated by various translations (bolded and underlined for emphasis).
“For the music director, written by the LORD’s servant, David; an oracle. An evil man is rebellious to the core. He does not fear God…” (NET)
“For the director of music. Of David the servant of the LORD. I have a message from God in my heart concerning the sinfulness of the wicked: There is no fear of God before their eyes.” (NIV)
“For the choir director. A Psalm of David the servant of the LORD. Transgression speaks to the ungodly within his heart; there is no fear of God before his eyes.” (NASB, ESV)
In Hebrew, the word between the title and first verse is translated above as “oracle, message, speaks.” The first question is whether it is meant to be part of the title (NET), the introduction to the psalm (NIV), or part of the psalm itself (NASB, ESV). The second question is whether this was in the evil man’s heart (NET, NASB, ESV) or in David’s heart (NIV). Constable and Ross (Bible Knowledge Commentary) prefer the NIV understanding that this is a message David received from God in his own heart, and I agree. The message God gave David about an evil man is this: “He does not fear God” or, literally (as the other translations show), “There is no fear of God before his eyes.” Solomon states that this deficiency is the basis for the lack of knowledge and wisdom (Proverbs 1:7; 9:10) but mostly that “The fear of the LORD is to hate evil” (Proverbs 8:13), the antithesis of the evil man.
This evil man is described in Psalm 36:2-4. The actions listed are the results of his lack of fear for God. At its core, this is a description of a heart that is far from God. It explains God’s judgment of the global Flood (see Genesis 6:5) and is summed up (almost understatedly) in Jeremiah 17:9 – “The heart is more deceitful than all else and is desperately sick; who can understand it?” (NASB)
Yet, in spite of man’s innate rebellion against God, he continues to extend his “loyal love…faithfulness” to all of mankind (Psalm 36:5-9). His “justice” was demonstrated on the cross, and in his “fairness” he condemned every person while, at the same time, extending salvation to each one individually and equally (Romans 11:32). All can believe in him and find “shelter…food…drink” as he “sustains” them.
David concluded with a plea that God would take special note of his “faithful followers” and vindicate them when they are abused by those who do not follow him, something God has repeatedly promised to do (Psalm 36:10-12).