Rom 1:17 For in it the righteousness of God is revealed from faith for faith, as it is written, "The righteous shall live by faith." (ESV)
The revelation of the righteousness of God is important to note. God is righteous and just, yet because of all the injustice and evil in the world, some conclude that He is not. It is in the gospel that God's righeousness is being revealed from faith to faith. That is, His righteousness is revealed to those who believe, and it continues to be revealed to believers in the gospel.
Not only that, but believers live by faith through the righteousness of God. God's righteousness is received as a gift by faith (Romans 3:22,24;5:17). The believer also lives as a righteous person before God (Romans 5:19,21), because God's righteousness is imputed to him or her by their faith or trust in Him (Romans 4:5). The only way for a sinful person to be made righteous before God, Pual tells us, is by faith alone in this gospel for which there is no reason to be ashamed (Romans 1:16).