Jesus said to his disciples:
"Do not think that I have come to abolish the law or the prophets.
I have come not to abolish but to fulfill.
Amen, I say to you, until heaven and earth pass away,
not the smallest letter or the smallest part of a letter
will pass from the law,
until all things have taken place.
Matthew 5: 17-18
But what does this mean for us, the latest in a long line of gentile converts to Christianity, grafted onto the faith of Abraham by our baptism? Surely we have not followed the Law that God gave to his people through Moses! So what does it mean when Jesus says that he has not abolished, but fulfilled the Law, and that none of it will pass away?
There are lots of angles on this, but here's the one that works for me: the Law was a gift to the people, that they might imitate the holiness of God. "Be holy as I am holy." Now everyone who has tried to live a holy life knows the experience of mixed results. Our attachments, sins, and unconscious motivations often make a mockery of our desire for holiness and devotion, and we find ourselves in the discouragement of desiring God but being stymied by our own inability to seek Him devoutly.
The gift of the Incarnation is a remedy for this sorry condition. Jesus, in his divine humanity, mirrors the holiness of God from within our human condition, and offers the perfect sacrifice of obedience to the Father, thereby justifying our humanity before God. Thus the holiness we could not attain on our own has been accomplished on our behalf by one like us in all things but sin.
At this point we must be careful not to make the protestant error which sometimes seems to say that we remain in our miserable state of utter failure even though we are justified before God in Christ. Not necessarily! We in the apostolic churches--and in some ways the Orthodox even more than us Catholics--have what one of my teachers called a "maximalist anthropology." We believe that the human person can be redeemed and lifted up to sanctity in Christ. This is because Jesus has allowed the blessing and grace of his perfect sacrifice and holiness to pass over into us through the Resurrection. This is exactly what we mean by the coming of the Holy Spirit as the animator of the Church, and by the Eucharist as the living memorial of the Passion. Jesus has handed over the fruits of his own perfect sacrifice into our hands, that we too might fulfill the Law through him, and become holy as God alone is holy.