What does Psalm 7:9 mean?

David observes that the righteous God tests minds and hearts. He knows what every person is thinking, and He discerns the thoughts and motives of every person's heart (Psalm 139:1, 4, 23–24; 1 Samuel 16:7). In the time of Noah, 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" (Genesis 6:5). David's primary purpose here is to continue asking God for judgment on those who have brought false accusations (Psalm 7:6–8).

Human judges may make mistakes, even if their intentions are good. They might sincerely be mistaken, rendering an unfair verdict and sentencing the one pronounced guilty. God, however, never makes a mistake. His judgment is always right because He is perfect. There is no trace of sin in Him. As this verse notes, God will one day end all evil, and those who honor God will be secure forever.

Jesus, the Son of God, will judge the world in righteousness (Acts 17:31); He is qualified to do so because He is completely righteous. Even Pilate, who consented to Jesus' crucifixion, said, "I find no guilt in this man" (Luke 23:4). The apostle Peter describes Jesus as "a lamb without blemish or spot" (1 Peter 1:19).