Before we can begin a serious investigation into Paul's misuse of the Jewish Scriptures in his denigration of the Jewish Law in developing his "new religious" synthesis in the New Testament I feel it is necessary to discuss in summary fashion the relationship of faith and obedience to the doctrine of salvation as found in the Jewish Scriptures.
So much has been said about salvation and faith in terms of Paul's Christological doctrines that it might be interesting to summarize here a Jewish understanding of these spiritual concepts.
No one has given a more succinct and precise interpretation of what salvation means to Jews than the Christian theologian, E.P. Sanders. He explained it this way:
Salvation comes by membership in the covenant while obedience to the commandments preserves one's place in the covenant (E. P. Sanders, Paul And Palestinian Judaism, pp. 419-422). A Jewish scholar, H. J. Schoeps, emphasized the partnership character of the brit or covenant, as involving mutual obligations between God and Jews (H. J. Schoeps, Paul, p. 218). The Torah and covenant are juxtaposed because they are so closely connected. When the prophets berated Israel for transgressing the law, they spoke of breaking the covenant. It was that brit which assured Israel of her redemption (salvation) by God since that was His side of the bargain.
Paul emphasized faith and placed it in opposition to the Law. A person who knew nothing about Judaism (the typical uneducated Christian concerning the basic religious tenants concerning Judaism) could easily get the impression that faith was antithetical to that religion. Paul's doctrine of faith versus law is based on a fallacious assumption that faith excludes law (E. P. Sanders, Paul, the Law, and the Jewish People, p. 20). This polarity of faith and the law is contrary to the continuous meaning of the Bible narrative and unintelligible to the Jewish reader. Even in the Midrash the merit of faith and the merit of obedience to law are set along side each other and not played off against one another. Faith stemmed from fidelity to God and His law.
Quite apart from scholarly statements, the piety and devotion of Jews to their Torah through three-and-a-half millennia of adversity, exile, and persecution stands as testimony to their faith. No other proof or learned pontification is as strong or convincing as this empirical evidence.
To fully understand these critical issues I highly recommend that you purchase and read completely these books by E. P. Sanders because in so doing you will be able to see and grasp the deviation of Paul from Biblical Faith. Failure to possess such information concerning what the Jewish Scriptures teach about the relationship of faith and obedience in relation to salvation has caused untold millions to read the Pauline literature and never notice that his "gospel" is a direct contradiction of what God has said from Genesis through Malachi.