All of these Psalms are written by King David. Many of them are confidence Psalms, where David puts his confidence and trust in the Lord. We also see the difference between the wicked and the righteous. Psalm 16 is referenced by the Apostle Peter in his first sermon in Acts 2:25-35 and by Paul in Acts 13:35, and they say that David's body died and decayed, but the Lord Jesus did not because God raised Him from the dead. It is through Jesus that we have forgiveness of sins. Psalm 20 is a Psalm of the King going to battle, and Psalm 21 is the victory of the King as he comes home. The King has victory because he trusts in the Lord.
