A question has come up from an insightful reader. Did Jesus really abolish the Old Law?
Of course, we must not agree with the Lutheran thesis that observance of the commandments is no longer a “way and condition of salvation”. For the Catholic Church teaches that such observance is indeed a “way and condition” of salvation. See Veritatis splendor, art. 12. Irenaeus most helpfully teaches that Jesus re-affirms the core commandments and makes them even more stringent. I.e. the Sermon on the Mount is more rigorous. Thus, we see one element of the meaning of “fulfillment” in Mt 5:17. Jesus does not leave us with a religion void of those core commandments but in fact with one replete with the inner and the outer.
Nevertheless, the entire Old Law was issued by Moses. Although that which is commanded in the core commandments is also commanded by Jesus, the Old Law is itself abrogated by Jesus, the founder of our religion. Pius XII, Mystici corporis, art. 29, citing back to Leo the Great (sermon LVIII):
And first of all, by the death of our Redeemer, the New Testament took the place of the Old Law which had been abolished; then the Law of Christ together with its mysteries, enactments, institutions, and sacred rites was ratified for the whole world in the blood of Jesus Christ. For, while our Divine Savior was preaching in a restricted area – He was not sent but to the sheep that were lost of the House of Israel  – the Law and the Gospel were together in force;  but on the gibbet of His death Jesus made void the Law with its decrees  fastened the handwriting of the Old Testament to the Cross,  establishing the New Testament in His blood shed for the whole human race. “To such an extent, then,” says St. Leo the Great, speaking of the Cross of our Lord, “was there effected a transfer from the Law to the Gospel, from the Synagogue to the Church, from the many sacrifices to one Victim, that, as Our Lord expired, that mystical veil which shut off the innermost part of the temple and its sacred secret was rent violently from top to bottom.” 
Thus we see the second meaning of “fulfillment”. That which was shadow must pass away when that which is its reality comes.
Israel is first in the order of pedagogy and development, just as matter is first in the order of natural development and just as individual things are first perceived by the senses before words can make any sense at all. You don’t know what “ball” means until you see many of them. Israel was preparation for the reality. Forgiveness of sins was not offered through the sacrifices of the Old Law except, as it were, in a manner of a plea, by anticipation of the coming Cross of Christ.
Christ is first in the order of excellence and nature, just as form is first in terms of ontological priority.
So we come to the question: Did Christ found a new religion?
Well, in that Israel was the expectation of him, in that it was divinely appointed to expect him and to prepare the minds and hearts of many for his appearance, no. In this sense, he comes to be the substance of what Israel was in shadow. And in this sense, there is significant continuity. According to the flesh, he is son of David.
But in that he is the Incarnate Son himself, he by his own authority establishes his religion. He does not “hearken” to any man’s voice but only to the Father. Thus, his religion is the radical foundation. Just as form — not matter — is the radical foundation of entity, so Christ — not the shadows anticipating him — is the radical foundation of the Christian religion. He has no foundation beneath him. And since he himself in his flesh founds this religion, it is new with him and it is a new religion.
But this second consideration throws the question into new relief. For it exhibits that insofar as Israel was truly a divinely appointed religion, it is the im-perfect form of the religion Christ establishes. In this sense, he does not form a new religion parallel to the old (yet superior). Rather, the old is in fact — in the order of divine intention and in the order of excellence and nature — subsequent to that of Christ. This is to say that Israel is built upon Christ, not Christ upon Israel.
There may be an analogy with evolution provided we understand it as directed by God as transcendent cause. The former stage is for the latter stage. If indeed we have evolved, yet are standing now erect and thinking, we are the reality not the previous stages as such. And we are that reality by our human souls. And our human souls do not evolve. They are im-material. But everything that evolves is material. It is matter brought to form through processes. But what is im-material cannot be “brought” to be through the manipulation of matter. At each transition, the former is for the latter. The former is the disposition to the latter. Yet the latter is the reality with respect to the former. So too, Christ is not the product of Israel. He is not appointed by Israel. He is its foundation and chief, the only true door to salvation. Christianity understands itself to be thoroughly Jewish in that Judaism had nothing false in it; only truth; and divine truth. This truth finds its true foundation in Christ Jesus, not a mere man and not a mere angel and not only God, but the God-man.