In other words, every new exercise of faith in God and in his great precepts and promises, which is the true idea of religious faith, increases the strength of the principle of faith. This is, practically, a very important view; and especially to those who are desirous of living a truly holy life. I am aware that the increase of religious faith, as well as its origin in the first instance, is the gift of God. But God very properly requires us to observe the laws of our mental nature, and to do what it is our privilege to do.
Accordingly the blessing of God, manifested in the increase of religious faith, seems to me, as a general thing, to conform to this view; and that those and those only who, in observance of the natural law, diligently exercise the faith they already have, can reasonably expect to have more, either by natural increase or by special grace. And, indeed, the doctrine which has now been advanced will apply to all the Christian graces, since God no where gives encouragement, so far as we can perceive, that he will add to the possessions of him who misimproves even his one talent. “For whosoever hath, to him shall be given, and he shall have more abundance; but whosoever hath not, from him shall be taken away even that he hath.” Matthew 13:12.
— edited from The Life of Faith (1852) Part 1, Chapter 3.