What does Psalm 21:11 mean?
The assembled people are celebrating God's favor for David (Psalm 21:8–10). They are confident that those who try to defeat the king will fail.God knows the intentions of evil men and women as surely as He knows their sinful deeds. In Noah's day civilization had descended into a quagmire of wicked intentions as well as depraved behavior. The Lord saw this wickedness. Genesis 6:5 reports that "the LORD saw that the wickedness of man was great in the earth, and that every intention of the thoughts of his heart was only evil continually." The Lord responded to those evil intentions and wicked deeds by sending a devastating flood to destroy the wicked.
Jeremiah 17:9 describes the human heart as "deceitful above all things, and desperately sick." The same verse raises the question, "Who can understand it?" The answer appears immediately afterwards: "I the LORD search the heart and test the mind" (Jeremiah 17:10). No human can read the intentions of another person's heart, but the Lord can (1 Samuel 16:7). He knew what David's enemies were planning, and He would cause them to fail.