Romans 4 continues the theme of justification by faith, which Paul introduced in Romans 1:17: "The righteous shall live by faith." (ESV) Romans 5 builds on the concepts of justification by faith which are discussed in chapter 4. Romans 5 begins, "Therefore, since we have been justified by faith, we have peace with God through our Lord Jesus Christ." (Romans 5:1 ESV) Clearly, the theme of Romans 4 is “justification by faith.”