There is much confusion in the religious world around the topic of the two covenants. Most people do not have a proper understanding of the two Covenants and how they relate to each other.
In Romans 7:1-7, Paul uses the divine institution of marriage to teach us about the duration of the Old Law. He tells us that a woman is bound to her husband as long as he lives. Therefore, she is not free to marry another man until her husband dies, lest she should be called an adulteress. He then applies this lesson to the two covenants.
He tells us that we have become dead to the law (Mosaic Law) by the body of Christ. Colossians 2:14 tells us that Jesus nailed the Old Law to his cross. This fulfilled the prediction that he made in Matthew 5:17-18. He did not come to destroy the Law but to fulfill it down to the very finest detail.
Paul also said that the Law was to last "till" the seed should come (Gal 3:19). That seed was Christ (Gal 3:16).
Since the Old Law has been fulfilled, we are free to marry Christ. That marriage takes place when we obey the gospel (2 Cor 11:2). Not only are we free to marry Him, but we must if we desire to be saved.
However, there are many who are not satisfied with being married to Christ alone. They desire to be married to the Old Law as well.
Some will argue that only the ceremonial Law was removed while the Ten Commandments are still enforced. This explains (in their minds) why sacrifices are no longer made.
However, Paul points out in Romans 7:7 that the "Law" told him not to covet. This was one of the Ten Commandments. Therefore, if the Law was fulfilled and done away with, it included the Ten Commandments.
This is not to say that the Old Testament is not valuable, for it truly is (Romans 15:9). However, we do not look to it for salvation; that is found only in the New Covenant (Hebrews 10:1-4).
-- Ralph Price --