Romans 4 - Jewish Righteousness by Belief yielding Obedience equals “Grace by Faith and not by Works”
In teaching of a new righteousness and calling it justification, what is Paul really doing? He is teaching of a new delivery system for righteousness… Christ’s sacrifice. Before then, belief and obedience toward God meant believing the Law of Moses and living it. However, God never actually said to believe the Moses per se, but to believe God; and obedience was never meant to be to the Law per se either, but to God who is the Law’s source. Paul realizes this and spends chapter 4 of Romans making this clarification:
  1What then shall we say that Abraham, our forefather, discovered in this matter? 2If, in fact, Abraham was justified by works, he had something to boast about—but not before God. 3What does the Scripture say? “Abraham believed God, and it was credited to him as righteousness.”
This is exactly where we started in Guidelines for Righteousness:
Genesis 15:6
Abram believed the LORD, and he credited it to him as righteousness.
Now, to a Christian, belief is by faith, because we believe things that are known only through the spirit. As it turns out, these spiritual truths tend to manifest in physical ways, making it quite easy for us Christians to continue on in our faith, but these physical manifestations are generally not enough by themselves… faith is usually a necessary prerequisite. And Abram believed by faith. Paul goes on…
 4Now when a man works, his wages are not credited to him as a gift, but as an obligation. 5However, to the man who does not work but trusts God who justifies the wicked, his faith is credited as righteousness. 6David says the same thing when he speaks of the blessedness of the man to whom God credits righteousness apart from works:
 7“Blessed are they
      whose transgressions are forgiven,
      whose sins are covered.
 8Blessed is the man
      whose sin the Lord will never count against him.”
And so Paul makes the case that when God is crediting righteousness to a man on account for his belief, what God is really doing is pardoning Him from punishment for sin; he is not receiving that pardon by works, but by faith (i.e., “belief”). Pardon from what? Well, back in Genesis 12, Abram failed to trust God when he was a guest of a king. He told the king that Sarai was his sister, a technical truth, but a practical lie, for the king took Sarai as his concubine as a result, something he would have never done had known she was Abram’s wife.Â
Abram misled because he failed to trust God.Â
After failing to trust God before, Abram chooses to trust God now. And which is easier do you think? to believe that God will protect you from kings, or that he will give your wife a son in old age? Well after failing in the first point, Abram believes God on the second, and God credited that to him as righteousness. In doing so, God was choosing to no longer see Abram the liar, or Abram the distrustful. He saw Abram the faithful. And so we see Paul is right. God was taking a man who deserved punishment for sins against God, and justified him. In fact, recall just who would eventually come through that promised seed, to die for Abram’s sins… why, Jesus of course.
Now, in Paul’s time, justification from God was only thought by Jews to be for Jews… so when Jews came to know Jesus, they saw the fulfillment of their Jewish faith in Christ… but then what of the gentiles? Well, they had no covenant with God that Christ’s sacrifice would fulfill.  Guess what! Abram didn’t have a covenant (yet) either! How do we know? Because circumcision was the sign of that covenant, and Abram was not yet circumcised. For someone in Paul’s time then, it reduces the question to whether salvation is for the uncircumcised…
 9Is this blessedness only for the circumcised, or also for the uncircumcised? We have been saying that Abraham’s faith was credited to him as righteousness. 10Under what circumstances was it credited? Was it after he was circumcised, or before? It was not after, but before! 11And he received the sign of circumcision, a seal of the righteousness that he had by faith while he was still uncircumcised. So then, he is the father of all who believe but have not been circumcised, in order that righteousness might be credited to them. 12And he is also the father of the circumcised who not only are circumcised but who also walk in the footsteps of the faith that our father Abraham had before he was circumcised.
We see then that God will justify those under the law as much as those who are not. It merely starts with belief, or faith.
 13It was not through law that Abraham and his offspring received the promise that he would be heir of the world, but through the righteousness that comes by faith.
Now here it could get a little confusing for a believing Jew: what then of the law? Is Paul saying that righteousness does not come from the law? Well, as we have seen before, following the law as at most obedience, and while obedience is the substance of our righteousness, it is not the source of it. Recall Deuteronomy 6:25:
And if we are careful to obey all this law before the LORD our God, as he has commanded us, that will be our righteousness.
So, if belief is accounted to us as righteousness and obedience is merely its outward sign, then following the law cannot earn you a place in Heaven, as Paul goes on to explain.
14For if those who live by law are heirs, faith has no value and the promise is worthless, 15because law brings wrath. And where there is no law there is no transgression.
Now, Paul here is talking of legal transgression, not sin per se. Where one transgresses God’s law to them, they are in sin, but Abram’s lack of trust in God was no less sin than the transgression of law. But Abram’s justification by God, his righteousness, was through mere belief, the kind Christians have come to call “faith”, as Paul goes on to explain…
 16Therefore, the promise comes by faith, so that it may be by grace and may be guaranteed to all Abraham’s offspring—not only to those who are of the law but also to those who are of the faith of Abraham. He is the father of us all. 17As it is written: “I have made you a father of many nations.”[c] He is our father in the sight of God, in whom he believed—the God who gives life to the dead and calls things that are not as though they were.
And now I think I’ll let Paul close this out…
 18Against all hope, Abraham in hope believed and so became the father of many nations, just as it had been said to him, “So shall your offspring be.”[d] 19Without weakening in his faith, he faced the fact that his body was as good as dead—since he was about a hundred years old—and that Sarah’s womb was also dead. 20Yet he did not waver through unbelief regarding the promise of God, but was strengthened in his faith and gave glory to God, 21being fully persuaded that God had power to do what he had promised. 22This is why “it was credited to him as righteousness.” 23The words “it was credited to him” were written not for him alone, 24but also for us, to whom God will credit righteousness—for us who believe in him who raised Jesus our Lord from the dead. 25He was delivered over to death for our sins and was raised to life for our justification.