What connection is there between the “natural moral law” and the Law of the Old Covenant?
The Law of the Old Covenant expresses truths that by nature are evident to human reason yet are now proclaimed and authenticated as God’s Law.
What significance does the Law of the Old Covenant have?
In the Law (the Torah), and its centerpiece, the Ten Commandments (the Decalogue), the will of God is manifested to the people of Israel; following the Torah is for Israel the central way to salvation. Christians know that we can tell by the Law what ought to be done. They also know, however, that it is not the Law that saves us.
Every man has the experience of finding that something good is, so to speak, “prescribed”. But one does not have the strength to accomplish it; it is too difficult; one feels “helpless” (see Rom 8:3 and Rom 7:14-25). One sees the Law and feels that one has been handed over to sin. And so precisely through the Law it becomes clear how urgently we rely on inner strength in order to fulfill the Law. That is why the Law, as good and important as it is, only prepares the way for faith in the saving God.