Martin Luther: Here's what spawned the reformation via Martin Luther.
Martin Luther, Commentary on Romans(Grand Rapids: Kregel Publications, 1976), xiii.
He was a pios, earnest monk--an apparent Christian. But Luther had no peace of soul. He wanted to please God, to be accepted by Him. But the harder he worked the more elusive the salvation of his soul became. Instead of growing closer to God, he found himself moving away from Him. Instead of coming to love God, which Luther knew he should do, he found himself hating God for requiring an apparently impossible standard of righteousness of human beings. In desperation Luther turned to a study of Paul's great letter to the Romans where, as early as the seventeenth verse of chapter 1, he found the solution: :In the gospel a 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."
As God opened the meaning of this verse to Luther, he realized that the righteousness he needed was not his own righteousness but God's righteousness freely given to all who would receive it. Moreover, this was to be had, not through any works of his own but by faith only. It was by taking God at His word, by believing Him. Luther did this and felt himself to be reborn.
Here is how he put it: "I had no love for the holy and just God who punishes sinners. I was filled with secret anger against Him: I hated Him, because, not content with the frightening by the law and the miseries of life us wretched sinners, already ruined by original sin, He still further increased our tortures by the glospell...But when, by the Spirit of God, I understood the words, --when I learned how the justification of the sinner proceeds from the free mercy of our Lord through faith...then I felt born again like a new man...In very truth, this language of St. Paul was to me the true gate of Paradise."