“By grace you have been saved through faith, and that not of yourselves; it is the gift of God” (Eph. 2:8)
The gospel is the power of God unto salvation to everyone who believes. “With the heart one believes to righteousness” (Rom. 10:10). “This is the work of God, that you believe in Him whom He sent” (Jn. 6:29). Faith works.
Time would fail to tell of those ‘who through faith subdued kingdoms, working righteousness, obtained promises,…out of weakness were made strong” (Heb. 11: 33,34). People may say, “I cannot see how it is possible for one to be made righteous simply by believing.” It makes no difference what you can see; you are not saved by sight, but by faith. You do not need to see how it is done, because it is the Lord who does the saving. Christ dwells in the heart by faith (Eph. 3:17), and because He is our righteousness. “He also has become my salvation” (Isa. 12:2).
If when the preaching of the gospel reveals to us the law of God, we reject it and find fault with it because it condemns our course, we are simply saying that we do not desire that God should put His own righteousness upon us. But, as we receive Him by faith, and we walk in Him as we have received Him, we shall “walk by faith, not by sight” (2 Cor. 5:7).
If in anyone who has sought righteousness through Christ there is afterward found sin, it is because the person has dammed up the stream, allowing the water to become stagnant. Where there is no activity there is death. No one is to be blamed for this but the person himself. Let no professed Christian take counsel of his own imperfections and say that it is impossible for a Christian to live a sinless life. It is impossible for a true Christian, one who has full faith, to live any other kind of life.
Waggoner, Waggoner on Romans, p.22