t is one thing to believe that God is willing to forgive sins. It is quite another thing to recognize that I am currently in need of His forgiveness. Yet, neither of those two commendable realizations are enough to complete the transaction. God has to do something to make forgiveness available... and, we have to do something to make it applicable. For us to be forgiven, God has to justify us... He has to simply declare that we are righteous, although we know that we are not. Enters: redemption through the blood of Christ (Romans 3:24-26). Not that David or other Old Testament saints knew how God was going to put their sins away... then again, maybe they did. But either way, however He was going to do it, God had to be their justifier. David had to have known that much, because he said so in Psalm 32:1-2.
But wait a second, God's willingness to forgive and even God's provision for forgiveness (and even our knowledge of those things) does us no good unless we repent of our sin and confess it to God. Again, David hit the nail on the head in Psalm 32:5. Repentance and confession function as our signature on a contract of grace which was written by God alone and which He alone can execute.
Now, you might ask, "Where is faith in Psalm 32:5? Isn't faith also essential?" Indeed, it is! Faith in God is absolutely necessary (Hebrews 11:6, Romans 4:3, Galatians 3:6 & James 2:23). Faith may not be named in Psalm 32:5, but it is certainly present. Notice the 2 little prepositional phrases, "unto thee" and "unto the Lord" - David's confession UNTO the Lord implies clearly that God was the one in whom he trusted.