Where does faith comes from? God is the originator. He, God the Holy Spirit, produces faith in us, after He has changed our heart from rock to flesh. Ephesians, chapter 2:
We could debate that the word “this” is being applied to salvation only. But I think Apostle Paul has the whole process in mind: it starts because God is full of grace, the result is our salvation, and the instrument is faith. The whole package is a gift from God, not a result of anything we have done. Kind of remove a lot of pressure off our shoulders, doesn’t it?