I
just read a very interesting piece of theologizing that puts certain things about Christ's relationship to the Old Testament into clearer focus.
For the Israelites, relation to God was mediated by the Law that He formed for them. This Law was binding solely on His people, the Jews; and this Law (we could call it "positive law", in the sense that it is contingent) was how He was expressed to them, how they experienced their relationship with Him.
When the Son was made man in the person Jesus of Nazareth, we were given the riddle that He has both overturned the Law, freeing His people from it; and has fulfilled the Law, preserving every jot and tittle. How is this so?
By becoming Man, God has changed His relationship to us -- previously, the Hebraic Law was the mediator; now, it is the human body of Jesus Christ that is the mediator, and all who share in bodily humanness are invited into the new covenant. The basis of our relation and understanding of God has shifted. Before, adultery was wrong because it was written in God's Law. Now, adultery is wrong because the human body, with its male and femaleness, has become the literal sacred temple of God. Our motivations now are rooted in sharing in the divine essence through Christ, rather than strict obedience to an authoritative will.
This is a very powerful idea, that I believe seeks to explain the way in which Christian morality is different from Old Testament morality, while keeping continuity with it. I'll have to do some more research to see overall how convincing it is on the whole, and in particular have to read more St. Paul (whom I haven't paid his due quite yet with my attention).