Why Am I Thus? - The Battle With Indwelling Sin in Romans 7

There is in each one of us a law of sin. It may always be seen even when it is not in active operation, if our eyes are lightened. Whenever I hear a man say he has no propensity to sin, I infer at once that he does not live at home. I should think he must live a long way from home, or else he has never been anywhere except in the front parlour of His house where he keeps his profession. He cannot have gone through all the chambers and searched them thoroughly, or he would somewhere have discovered that there is an evil heart of unbelief in departing from the living God. This is true of the believer; he has to cry out against another nature, and say, "Help thou mine unbelief." It is always in the man.