First, the book of Romans is talking about the heresy of trying to be circumcised in order to be justified before God. So Paul's point is not that we are not to do NOTHING for our LORD in order to be right with Him. For even a belief is an action of some kind. The point Paul was making is that he was saying that Abraham believed God first and was justified and THEN....Abraham was able to perform (bring forth works being fully persuaded by his belief) so as to refute the belief that one has to be circumiced in order to be saved. For Romans says,
"And being fully persuaded that, what he had promised, he was able also to perform." (Romans 4:21).
"What advantage then hath the Jew? or what profit is there of circumcision?" (Romans 3:1).
Meaning, Abraham believed God and being fully persuaded by that belief he was able to perform. The performance part is not an option. For performance was a part of Abraham's faith. Paul's point here has to be in view of the fact that he was trying to refute "circumcision" in order to be justified before God.
However, if believers did not have to cooperate with God, then people could be their own masters and also serve God. But it doesn't work like that. Jesus said you cannot serve two masters. Repentance from sin and the fruits thereof (by turning away from sin) is a part of the salvation process. One cannot remain in their sins and think they are still saved. One cannot refuse to do good works in this life and still think they are saved.
Second, in Romans 4:2 is in view of initial salvation or in how one is ultimately saved and it is not talking about the good works of Christ that one would do over their entire lives. Again, Paul has "circumcision" (or in going back to the Old Law) in mind when he is saying this. So it should be read in that light. In other words, one does not need to first be circumcised in order to be initially saved. That is what Romans 4:2 is saying.
Third, technically speaking no man directed work will save anyone. For the key question one needs to ask is: Are we saved by man directed works or are we saved by God directed works? Well, according to the Bible, no outward obedience can save anyone. So I can say that Romans 4:2 is true. Man is not justified by keeping some kind of external form of work (like going back to circumcision) so as to be right with God. However, a person does need Christ (God) living within them in order to be saved, though. For 1 John 5:12 says,
"He that has the Son has life and he that does not have the Son does not have life." (1 John 5:12).
So if a person has Christ living within them, then the fruits or works of Christ will be evident in that person's life. So yes, we are not justified by any works before God (of our own doing) because it is God who is the One who ultimately does the good work in us.
James says we are justified by works. Not before men. We cannot justify our faith before men. Our justificaton and salvation has to do with God. James is indeed saying we are justified by works. But the key to understanding is to understand what TYPE of work is James talking about. Is James talking about man directed works or God directed works in a believer's life? Well, the short answer is that James is talking about God directed works. For no true believer does their own work. For Jesus said we can do nothing without Him.
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