“For I am not ashamed of the gospel, for it is the power of God for salvation to everyone who believes, to the Jew first and also to the Greek. For in it the righteousness of God is revealed from faith for faith, as it is written, “The righteous shall live by faith.”
This text from Paul’s epistle to the Romans changed a man, and that man in the hand of God changed the world of his day, and his influence has been felt to this day. Martin Luther, in his own words :
Martin Luther, born in 1483 in Eisleben, Germany, son of a miner was once caught in a horrific thunderstorm. He feared for his life and cried out to St. Anne, the patron saint of miners, saying, “Save me, St. Anne, and I’ll become a monk!” The storm subsided and he was not killed. He kept his vow and entered the Augustinean monastery. He had an astute mind and had become a theology professor at the University of Erfurt. At this time he was a God fearing man, but not a converted man. Luther had understood the nature of sin as few people in our day would and he had understood the holiness of God in a profound way, as few people would do today. But he did not know how to deal with his sin before a holy God. He knew that all his attempts at justifying himself before God were failing.
As he was studying the letter to the Romans, it was this text that made him understand for the first time God’s method of justifying sinners. Until then he had always thought of justification from the typical Roman Catholic works oriented perspective. It was this text in Paul’s letter to the Romans that helped him to see that a person’s justification before a just, righteous and holy God was not something that a man could achieve in his own efforts. It was something that God did for man, and which a man could only receive by looking to God by faith alone. When Martin Luther had understood the basis of the gospel, namely, that a person’s justification came by the grace and mercy from God alone, the foundations for a new mighty work of God were laid. A Holy Spirit sent revival had begun.
All because of Romans 1:16-17.
These words constitute the theme of Paul’s letter to the Romans. The whole letter to the Romans is about “the gospel of God”. That phrase is first used in v.1, in the opening statement : “Paul… called to be an apostle set apart for the gospel of God”. This is the reason that Paul wants to come to Rome.
The gospel is at the heart of evangelical theology. This explains the difference between evangelical Christianity and the Roman Catholic Church, and every other system of religion in the world which operates on the primary basis of works righteousness rather than a righteousness from God – a righteousness outside of ourselves!
I am not ashamed of the gospel
Why does Paul say this negatively? Why does he not say, "I am proud of the gospel”? This form of speech is known as litotes Litotes is a figure of speech in which a negative statement is used to affirm a positive sentiment. We use it often in our conversations e.g. we say, “I am not opposed to doing this” when we could have said “I can do this”. Paul may have said it like this because of the peculiar position in which the Roman Christians had found themselves. It was not easy to be a Christian in Rome. It still is not easy to speak about Christ for fear of ridicule or rejection. Looking at the gospel at face value, it would appear as "foolishness". Jesus was the son of a poor carpenter, with little means, with no formal education and with no political ambition or influence. His message was a stumbling block to Jews and folly to gentiles (1 Cor. 1:22). He was crucified as a common criminal. Such a man claimed to be the Saviour of the world and He claimed to be equal to God. All this was so absurd to Jews and Gentiles. With all these thoughts in mind it is easy to feel ashamed of the gospel. This is what Paul experienced and yet despite all this Paul was never ashamed of the gospel.
Here is the reason, as to why he says that:
“Because it is the power of God for the salvation of everyone who believes...”
Despite the fact, that the gospel may be resented by man, it does not deny the fact that it is powerful! It is clearly seen in the words and deeds of Jesus. His Word and His works changed the world. The gospel is the power (Gr. dunamis) of God. Knowing this Paul felt no need to be embarrassed for coming to Rome. He knew that in the gospel there is a power that would overwhelm proud Romans !
How does this power work? Paul give three answers.
(i) The Gospel provides the power to save (16a). What does the gospel do? It saves sinners from the coming wrath of God. And it saves in the fullest sense of that word, past, present and future. The gospel has the power to …Forgive sins (past)—Impart new life (present)—Admit into heaven (future).
(ii) The Gospel provides the power to save those who believe (16b) To “believe” means to make a personal commitment to the God who has given us the gospel. It is not enough to hear and to pray a sinners prayer. The gospel must be believed in the fullest sense by hearing it, receiving it and by a continual walking in its truth.
(iii) The Gospel provides the power to save everyone who believes 16c : “For I am not ashamed of the gospel , for it is the power of God for salvation to everyone who believes, to the Jew first and also to the Greek.” The gospel has the power to save all kinds of people in the world without regard to the distinctions that divide us. That’s why Paul wasn’t ashamed to preach the gospel in Rome. He knew it had the power to save anyone who would believe it.
In verse 17 Paul reveals the second reason why he wasn’t ashamed of the gospel. “For in it (i.e. the gospel ) the righteousness from God is revealed, a righteousness that is by faith from first to last, just as it is written, ’The righteous will live by faith.’” This is the text that woke Martin Luther up from the dead ! Why is this such a powerful truth ?
(i) Because it reveals a righteousness (17a). The key word here is righteousness, which means to have a right standing in God’s eyes. Here is where the greatness of the gospel is clearly seen. It provides for us what we could never provide for ourselves. Righteousness is what we need but do not have. Therefore God, knowing that we could never be righteous on our own, has provided a righteousness which comes from Him, given to us as a free gift through Christ .That brings us to the second reason why the gospel is so powerful.
(ii) Because the righteousness that is in the gospel is received only by faith. (17b) The key word here is faith. In the Greek, it literally reads, “is revealed by faith unto faith.” (ESV) It has the idea of “faith from first to last.” Everyone who is saved by the gospel is saved the same way: By faith. It is faith alone and faith always. This answers the great question, How can I be right with God? The answer is simple: By receiving the righteousness of God that comes only by faith in Jesus Christ alone. He is our substitute. He alone has righteously kept the righteous law of God in His life. You have broken the law so many times, and in God’s eyes you are unrighteous. But God in His great love gave His Son, the Lord Jesus, the Righteous One to die the death that you deserved to die. All that God now requires of you is to have faith in Jesus- to trust Him with your whole life. He is the object of your faith.
There is a third and final reason why the gospel is so powerful.
(iii) Because the righteousness that is in the gospel, which when believed in, conveys saving faith to men and women. (17c) To prove his point Paul includes a quotation from the prophet Habakkuk 2:4: “The just shall live by faith.” It was this text—quoted by Paul in Romans 1:17—that ultimately shook Martin Luther to the core and brought him to saving faith in Jesus Christ.
FAITH ALONE !
From that simple and yet profound truth, came the Protestant Reformation. It saved the world from the hopeless doctrine of salvation by a system of works or self- justification. It restored the biblical doctrine of “Faith” as the operative principle by which men and women would be saved, and so with it the battle-cry of the Reformation became SOLA FIDE - “by faith alone.”
So, how much faith does it take to go to heaven? The answer is this : With whatever you have you must look to Jesus! Saving faith is putting your trust in Jesus Christ and Him alone. In order to do that you have to stop trying to save yourself.
What happened to Martin Luther can happen to you. Those who trust in Christ alone will never be put to shame, not in this life nor in the life to come.
 Luther's Works, Volume 34, P336-337). cited in http://christianity.stackexchange.com/questions/8742/when-and-how-did-martin-luther-arrive-at-the-justification-by-faith
 see Paul's arguments in 1 Cor 1:18-31