“For I am not ashamed of the gospel of Christ: for it is the power of God unto salvation to every one that believeth…. For therein is the righteousness of God revealed from faith to faith: as it is written, The just shall live by faith” (Rom. 1:16,17).
The reason Paul wasn’t ashamed of the gospel of salvation is that it reveals the righteousness of God. That is, the gospel of “Christ died for our sins” (1 Cor. 15:1-4) reveals how God doesn’t unrighteously sweep our sins under the rug and sneak us in the back door of heaven when the devil isn’t looking. He can righteously save us because His Son died to pay for our sins.
Then when we believe the gospel of salvation, God faithfully saves “whosoever shall call upon the name of the Lord” (Rom. 10:13). If you’re wondering why He has to say that, and why He might be tempted to do otherwise, it is because of the kind of people who sometimes call upon Him! You or I might have second thoughts about saving the likes of men like Saul of Tarsus or Jeffrey Dahmer, the serial killer cannibal who is said to have believed the gospel before he died. But God faithfully saves all who put their faith in Christ.
And that’s how the gospel is the power of God unto salvation “from faith to faith.” The word “faith” can mean faithfulness, as it does in Romans 3:3. So Romans 1:17 is saying that salvation flows from God’s faithfulness to save anyone to any who put their faith in Christ–from His faith to our faith. source