Faith, its role in salvation
"If I find a mother weeping over the account of the death of her first-born, which I know to be a false report, am I to be considered as a very adventurous prophet, or extravagant promiser, if, when I lay before her the proof of his being in perfect health, I make the declaration before hand, that if she believes my news, she will be saved from her sorrow, and that her heart will rejoice? Why, this is no more than what every reasonable being must regard as the necessary consequence of such a belief. Yet it is true, that she is saved from her anguish by faith in my story. But her joy is not a premium bestowed on her to reward her belief; it flows naturally out of her belief. Her grief for the supposed death of her child, and her belief that he is alive and well, cannot exist in her mind together. Such a faith necessarily heals such a sorrow. Her faith does not restore her son to life-- he is alive whether she believes it or not-- but his life is no joy to her, unless she believes it. Without faith in my story, she could not be saved from her distress." (Thomas Erskine, The Unconditional Freeness of the Gospel, pp. 18-19).
"Take another example. A son outrages in a most atrocious manner the feelings of his father. The father banishes him from his house, after pronouncing a malediction on him. The son hears of his death soon after, and feels his spirit burdened with the curse; he cannot shake himself free of it-- he is a miserable wretch. A friend of his father comes to him and tells him, that he had seen his father a few hours before his death, and that he had heard him express the warmest affection for him, and the deepest regret for what had taken place between them; and that he had received from him a charge to tell him, that he had withdrawn his curse, and had prayed a blessing on him. The son receives the intelligence with grateful joy, and his burden drops from him. He is saved by faith. His mind is healed by believing the information which has been given him. His father's forgiveness is not given him as a reward of his believing this history-- but unless he believes it, the forgiveness is quite useless to him-- he will continue to feel his father's curse clinging to him. But let me now here suppose for a moment, that the friend, instead of simply relating to him the fact of his father's forgiveness, had put the whole history into the form under which the gospel is very often preached: Suppose he had said to him, your father has forgiven you, if you believe in my testimony of his forgiveness; but if you cannot do this, there is no forgiveness for you. One can easily imagine the perplexity into which the son would be thrown by such an announcement. It would appear to him as if the truth of a past fact depended on the state of his feeling with regard to it. It would be impossible for him, in such circumstances, to believe, because his informant actually told him that his belief of the pardon must precede the existence of the pardon." (Thomas Erskine, The Unconditional Freeness of the Gospel, pp. 19-21).
"The use of faith, then, is not to remove the penalty, or to make the pardon better-- for the penalty is removed, and the pardon is proclaimed, whether we believe it or not-- but to give the pardon a moral influence, by which it may heal the spiritual diseases of the heart-- which influence it cannot have in the nature of things, unless it is believed." (Thomas Erskine, The Unconditional Freeness of the Gospel, pp. 22).