St. Augustine

8 For by grace are ye saved through faith; and that not of yourselves: it is the gift of God:
9 Not of works, lest any man should boast.

Have you ever notice the preceding words "For by grace are ye saved..." then it says "... through faith"? All of us who are Protestants or Evangelicals believe that salvation is by faith alone, as faith is the way to salvation and not by works. However, there iis a reason why grace proceeded faith

Augustine, or St. Augustine recognized the importance of Grace when he realized the truth of Original Sin which he personally evidenced in his life. Because of Original Sin, or what we call today as Sin Nature, we are naturally evil. It is not in us, to do good; ans so with that Augustine realized that the only way to be saved for God to do it Himself

God is the one who gives us the ability to believe as we are unable, and God is the one alone who is able to therefore save us as a consequence of our nature.

Luther recognised that truth as well as he also is a living evidence of his sinfulness. Both men and soon the Reformers used the word Depravity to denote the totality of their sinful state. And so, from Augustine, and continued by Luther and the reformers (all to a certain extent, some more than others) believed that salvation is givne by God's grace alone.

And when the debate arose between the camps of Arminians and Calvin, it resulted in maturing and biblical affirmation of Sola Gratia... grace alone.

Back to the scriptiure, many in the Calvinist camp recognize that if salvation is by grace alone, saving faith is a gift. It is a gift given by God in His sovereign will. Scriptures evidenced that people were saved not by their act of believing but by the choice of God such as in John 6:44, Acts 13:48, & Ephesians 1:5. Their inability which is why God ordain or predestined also evidneced in Genesis 8:31 & Romans 8:7.

But believing in that Sola does not affect your salvation. You are not saved by believing it, but it is historically part of the belief of the Reformers whilch is why it is part of the list of Soli..