The so called, “new perspective on Paul” movement has tried to diminish, as anachronistic, the view of Augustine, Calvin and Luther on imputed righteousness or accounted righteousness. While I appreciate and have gained much from the recent scholarship surrounding the faith and practice of the first century Jews, I think that the above mentioned idea that was set forth by E.P. Sanders et.al., is not borne out by scripture. Righteousness under the Mosaic Covenant was most certainly law righteousness that could only be expressed in self-righteousness.
First off, the Mosaic Covenant was ratified by the people of Israel. Exodus 24 explains the ratification of the covenant. Here is an excerpt:
(Exo 24:4-7 NASB) Moses wrote down all the words of the LORD. Then he arose early in the morning, and built an altar at the foot of the mountain with twelve pillars for the twelve tribes of Israel. (5) He sent young men of the sons of Israel, and they offered burnt offerings and sacrificed young bulls as peace offerings to the LORD. (6) Moses took half of the blood and put it in basins, and the other half of the blood he sprinkled on the altar. (7) Then he took the book of the covenant and read it in the hearing of the people; and they said, "All that the LORD has spoken we will do, and we will be obedient!"
The above passage shows the ratification of the Covenant and it was established in blood. In other words, it was a blood covenant or oath. Interestingly, they did not keep this covenant for forty days. When Moses went back up the mountain they sought out Aaron and entreated him to build a golden calf. This was quite likely no more than a week or two after Moses headed up the mountain. Aaron had to collect all the gold, fashion the calf and build an alter and that would have taken at least a week or two, probably more. We know that it was all done before the fortieth day because God told Moses what they were doing on the fortieth day (Exodus 32:7-8.)
Back to law righteousness… When Moses re-read all of the Law in Deuteronomy chapter six, the following was stated in verse twenty five. (Deu 6:25 NASB) "It will be righteousness for us if we are careful to observe all this commandment before the LORD our God, just as He commanded us.” There it is made very plain indeed that obeying the Law will result in righteousness under the Mosaic Covenant. This is exactly what promoted self-righteousness.
Now then, what does Paul have to say about this?
(Romans 10:1-4) Brethren, my heart's desire and my prayer to God for them is for their salvation. (2) For I testify about them that they have a zeal for God, but not in accordance with knowledge. (3) For not knowing about God's righteousness and seeking to establish their own, they did not subject themselves to the righteousness of God. (4) For Christ is the end of the law for righteousness to everyone who believes.
Paul states very clearly that Christ Jesus is the end of the Law for righteousness for everyone who believes. The righteousness of God, imputed righteousness is given based upon faith and trust in the gospel of Christ (2Cor 5:21.) For what purpose one might ask? That is a good question. The answer is to promote peace with God (Rom 5:1) that will translate into supernatural love for God. Resting in this supernatural love for God, will promote the loving heart that will be able to look at the commandments and see the heart of God and strive to obey. Not to be counted righteous but to please the Father they so dearly love.