When a person really believes that Jesus Christ is his Savior, God takes that person’s faith and counts it for righteousness. The person is not righteous; they have no righteousness of their own. They are still imperfect, still prone to sin, still short of God’s glory as sinful human beings. 

So how can we be made perfectly righteous? 

The gospel gives the answer. The gospel is the revelation of God’s righteousness. It reveals how we can be made righteous and reconciled unto Him