Helpful post by Bill Baldwin (Better Covenant), re: the Law of Christ transcending the Law of Moses:
There’s a new ethic in town. It’s an ethic that calls us to be as extravagant with one another as God has been with us. The Law can tell me to love my neighbor as I love myself. Only the Gospel–far transcending the Law–can move me to esteem you better than myself (Philippians 2:3). Moses commands us not to defraud. Only the Spirit of Christ could have made the churches in Macedonia give “beyond their means” (2 Corinthians 8:3). The Decalogue can order me not to murder. Only the love of Christ can compel me to lay down my life for the brethren (1 John 3:16).
This is the newness of the new commandment that Jesus gives in John 13. We are to love one another in the same way Christ has love us–humbling ourselves to the utmost as he did at his Incarnation, laying down our lives as he did at the cross. Moses never issued such a command. He couldn’t. The Law lacks that kind of moral authority.
The new commandment isn’t just another commandment to add to the list. The new commandment differs fundamentally, qualitatively, from all the old ones. The old commandments tell us of our obligation, of our duty. They push us to do right. The new commandment draws us forward to do more than mere duty. It calls us by the love of Christ to freely and cheerfully go beyond all commands. Anyone who seeks to fulfill the new commandment will naturally fulfill the old, and more besides. Anyone who pursues the old commandments will not even fulfill those.