There has been so much confusion recently over the way we are supposed to view the two testaments. This confusion has emanated from the pens of several very prolific theologians in the past decade. Without spending a great deal of time on the particular instances, I would like to offer a quote by Richard Gaffin in regard to the New Perspective on Paul. Gaffin writes:
One overall effect of the New Perspective tendency to reduce or moderate the distance between Paul and the Judaism of his day is that it appears to assume a basic continuity between the Old Testament and the various mainstreams within Judaism. For both James D.G. Dunn and N.T. Wright, two leading spokespersons for the New Perspective, the Old Testament roots of Paul’s theology and its roots in Second Temple Judaism seem to be interchangeable, or at least continuous. What one would think is an obvious distinction, at least from an evangelical perspective, is repeatedly glossed over. There is little appreciation or even recognition that Old Testament revelation and Jewish religion and theology are not the same thing and are often in conflict, even in Old Testament times and especially in Paul’s day. Nor is there an appropriate awareness of the canonical distinction of the Jewish Scriptures in relation to subsequent sources. The piety expressed throughout the Hebrew prophets and elsewhere in the Psalms, for instance, is normative in a way that the Qumran materials [those extra-biblical writings found in the Dead Dea Scrolls, produced by an apocalyptic sect at the time of Christ], are not, even when similar sentiments are expressed in the later. 
Gaffin’s analysis is profound. He has hit on two of the most, if not the two single most important elements of approaching a covenantal Bible. The first is the remnant principle. We cannot look at the writings of members of the covenant in an uncritical manner when we know that even during the Old Testament there were many covenant members who had departed from the pure, grace oriented, Christocentric understanding of Scripture. This is seen in Elijah and the seven thousand God had preserved from bowing the knee to Baal. It is also seen in the fact that Simeon and Anna were waiting for the Christ. When Anna finally sees Jesus she goes and reports to all “who were looking for redemption in Jerusalem.” Not all in Jerusalem were looking for the Chirst. Many were trusting in their own righteousness. This was not a matter of Jewish exclusivity. The parable of the tax collector and the Pharisee proves this. Both were Jews, both were members of the covenant. One was trusting in what he did. One was trusting in God to have mercy on Him.
The fact is, that there were Jews in the OT period and during Paul’s day that were not reflecting the religion of Scripture. That is, they were not part of the remnant of believing Israelites who were trusting in the Christ. Paul himself tells us in Romans 11:5 and 6, “At this present time there is a remnant according to the election of grace.”
Coupled with this, then, is the idea of a canonical approach to a covenantal book. If the Bible is structured by covenant, then we should expect this to serve as a safeguard against our introduction of extra-biblical materials into the hermeneutical process. The Jewish Scriptures were, by virtue of their covenantal nature, Christian Scriptures. They were always pointing God’s people to Christ. This is what we are told in Hebrews 11 about Moses, “By faith, Moses…esteemed the reproach of Christ greater treasures than the riches of Egypt.” We are told that David, “being a prophet, and knowing that God had sworn with an oath to him that of the fruit of his body, according to the flesh, He would raise up the Christ to sit on His throne. He, foreseeing this, spoke concerning the resurrection of the Christ, that His soul was not left in Hades, nor did His flesh see corruption (Acts 2:30-31).”
The point has not been sufficiently made that there was a right and a wrong way to interpret Scripture in the Old Covenant economy. Under the Old Testament there were believing Jews who were trusting in Christ and seeing how the Scriptures testified to Him (though they did not know when He would come or that His name would be Jesus). They knew more than we often credit them with knowing. This was possible by the work of the Holy Spirit in their hearts. But, there were also many–one could even argue most–Jews who did not understand the Jewish Scripture accurately. This is because they were kept blind to the Christological intent of prophetic word. This is precisely why we cannot put the Jewish Scripture on par with other Jewish writings–nor can we stress the need for Jewish interpretations of Scripture when the Bible gives us the interpretation in the pages of the New Testament. While even today we cannot simply accept whatever interpretations people in the visible church are promoting, it was the same in the OT and in the days of Paul.
 Richard Gaffin “A Reformed Critique of the New Perspective,” http://www.myteacherpages.com/webpages/MCSPELLMAN/files/A%20Reformed%20Critique%20of%20the%20New%20Perspective,%20by%20Richard%20Gaffin.htm