I once had a conversation with a waitress about how wonderful it is to live in Florida, particularly during the cold months of the year. This young lady indicated she was from the north, but, she said, "I wouldn't go back up north to save my soul." I said: "Well, you and I differ at this point. I have no desire to go back north either, but if it meant the saving of my soul, I wouldn't hesitate to go.
When we say, "I wouldn't do this or that to save my soul," we're speaking in a jocular fashion. I dare say those who use that phrase have not given any real thought to the literal meaning of their words. They are not making any kind of statement about their souls. They are simply using a popular expression.
But in the seventeenth century, the church and people in the wider culture were very much concerned with the salvation of the human soul. The Westminster Confession of Faith manifests this concern, setting forth the biblical requirements for salvation in some detail. In chapter 14, the confession lays out the key prerequisite for salvation. The title of the chapter is "Of Saving Faith," and it begins with these words: "The grace of faith, whereby the elect are enabled to believe to the saving of their souls, is the work of the Spirit of Christ in their hearts. . . ."
Take careful note of those first four words. The confession does not simply speak of faith. Rather, it calls our attention to "the grace of faith." It calls faith a grace because it comes to us as a gift from God—something that we cannot buy, earn, or merit in any way. The usual definition for grace that we have in theology is "God's unmerited or undeserved favor." So faith is a manifestation of the grace of God. Simply put, those who are saved are enabled or empowered to believe to the end of the salvation of their souls. Faith is not seen as an accomplishment of the human spirit. In fact, faith is not something that is naturally exercised by a fallen human being.
Herein lies the crux of the matter that provokes so much controversy in theology. On the one hand, God requires faith, and yet on the other hand, Scripture says that no one can exercise saving faith unless God does something supernaturally to empower or enable him to do so.