Matthew 5: 17-19 suggests a valid question often asked by Christian people - why aren't we keeping the Torah if Jesus so taught that in these passages? The passage in question reads, "Think not that I am come to destroy the law, or the prophets: I am not come to destroy, but to fulfill. For verily I say unto you, Till heaven and earth pass, one jot or one tittle shall in no wise pass from the law, till all be fulfilled. Whosoever therefore shall break one of these least commandments, and shall teach men so, he shall be called the least in the kingdom of heaven: but whosoever shall do and teach them, the same shall be called great in the kingdom of heaven.'
There is an answer to that but the backdrop of understanding is needed first. Of course, I need to say that what I have come to is very much in line with what the Church has come to, but I have deep conviction it is what Jesus meant at the time and what He means now. I need also to say, that sometimes the Bible is not understood deeply because it is treated as a book for the "now", instead of a book for both the "then and the now". And times change by the plan of God, and that is why there are covenants that are in biblical eras and frames.
People think that there are two covenants, the Old and the New. But actually there are many covenants (Britot), with their own times and requirements and meanings.
-There is the original one implied with the Creation of Man,
-there is the one with Noah and all mankind with the sign (Ot) of the Covenant, the rainbow, which God would see and "remember" His promise to not send another flood upon the earth.
-There is the covenant with Israel and the shedding of the Passover blood that Heaven would look at
-there was the covenant with Abraham with the sign of circumcision (which Moses was to forget to perform and his wife, Zipporah, to his shame, had to do for him);
-there was the giving of the Torah from Sinai (which people usually think of by the "Old Covenant"); and
-there is the New Covenant to come of Jeremiah 31.
-Then there is the time of fulfillment of the New Covenant with Jesus the Messiah, and the sign of this New Covenant - the bread and the wine, the Body and the Blood.
Furthermore, we can see that God relates Himself to people and the affairs of men differently in differing epochs and periods of covenant. For example, God, ever repugnant towards the shedding of blood in murder, at one period, places a particular mark on the forehead of Cain, to mark him out, precisely for protection, against "blood revenge". It is in His hands alone that just recompense is to reside. Lamekh feared, and rightly, that if the murdering of Cain would be avenged 7 fold, his murder of a man would be avenged 70 times 7. This was in Genesis 4. But in Genesis 7 we see transition to another epoch and another way of relating of God to man, and man to man. It was as if God's experience of man, through the whole period leading up to the flood and afterward, resulted in God modulating the exaction of Justice in the earth taking into account man's recalcitrance and hardness of heart. Now shedding of blood would be handled in a way other than a protective mark on the murderer that being in the hope that bloodletting would stop. Now the shedder of blood would have his own blood shed, and this, at the hands of man! Maybe that would work! And so the penetration and permutation of Justice in the earth, with all its difficulties involved, commenced and with it the institutions of justice on earth.
It is good for the understanding to see that covenants and epochs can be superseded by other covenants and epochs having other requirements, all leading to the goal and purpose that God has decreed. So we ought to expect movement in the course of the realization of God's plan.
And we can see movement, the calling of one man Abraham, than in the choosing of a people, and then a nation, then in the promise and push that all nations come to the God of Israel - that all nations be blessed in the seed of Abraham - which happens, no longer just prophesy, in the New Testament.
Jesus "ascended into a high mountain", just as Moses before Him had ascended Sinai, then He called his disciples to Him, He "sat down" - not an important thing to tell us except that Matthew, by this telling, tells us that this One now has the Authority, as sitting down in the fist century was the sign of the assumption of authority (seat of Moses), and "He opened His mouth and said" (He had to open His mouth in order to say, so why did Matthew write that? Because it is expressing a Hebrew way of telling us that the teaching to follow is authoritative - Vayaan vayomer (He responded and said). So who is this that gives the sermon on the Mountain? (the Gospel of Luke calls it the sermon on the "plain". Matthew points out it is a mountain, precisely because He is about to give the teaching (Torah) of the greater than Moses, Jesus. In actuality, the place is both a mountain and a plain, so both are right. It is on the north shore of Galilee, the only place on the sea where a mountain descends to a gentle plain until it touches the sea of Galilee.
All this is the Jewish way of biblical interpretation called "remez" (clue) [Matthew in many ways is the most Jewish of the Gospels] and is meant to tell us who Jesus is - He is the New Moses, the one, as the Messiah, who surpasses Moses, who is authorized of the Father to give the true or deepest or the now applicable meaning and intent of the Old Torah, for these new times and new era of the New Covenant, and so we hear Him, in this era, for this epoch that the disciples are about to enter (and in which we are found now).
"Do not think that I have come to abolish (really, "abrogate"") the Torah and the Prophets. The first eyebrow raiser. It was readily understood by Jews of the first century that "Torah" meant the commandments from Sinai, and that all the teaching of "Moses" was the content of Torah, so why was the need for adding "and all the prophets" except that it was not only "commandments" that were the object of His coming, but something, some element that was contained in the Prophets. So there is something deeper than "commandments" that Jesus is reaching for. The second eyebrow raiser - " I have come to fulfill". What does that mean? Rabbis could not say that they have come to "fulfill". The have come to keep, observe (lishmor), and to teach others to keep and observe. They are not come "to fulfill". A strange word! To fulfill (lemale') is to embody to the fullest, or, and here is the movement, to embody to the fullest and so to conclude, having brought to fruition. And if this be the case, than there is, not an abrogation, or an abolishing, nor a cancelling, and certainly not a forgetting or abandonment, but rather a discarding of a thing or way that has become obsolete - because it is not needed, its time is completed. Something else has come to carry on, and even to take higher, sometimes by piercing through to the original intent, sometimes by applying in a new way to situations not of the original. It was said, in another context, "Rabbi Meir - the peel of the fruit he threw away, and the insides he ate"
This understanding lays alongside of this fact - Jesus is teaching these things but, at the same time, He is speaking to disciples, and whoever listens in, all of the Jews, who are living not in the time of the New Covenant, but in the Time of Torat Moshe, the Old Covenant still in effect. Most people think that He is speaking to people of the New Covenant, to us. It is an indication of the authenticity of the Gospel material that Jesus is actually speaking to the people of His generation. He is not talking to Christians to come, not to us in the 20th, 21st century, but to the people of His own who are still living, as He is, in the time of the reign of the Law from Sinai, still in effect. So, of course, anyone who breaks or thinks of teaching others to break the commandments will be the very least in the Kingdom.
There will be a time when the Kingdom shall come in force and in full, but that is not now, or rather not then. Then was the Kingdom breaking in, with signs and signal of the fullness to come, when the Kingdom shall come in full power. But even now one can see the invasion - poor being preached to, the wounds being healed, the yoke being broken, the lepers healed, the dead raised. And where these break through, the new order has come, and the old obsolete. This is true. But this has a relationship to the keeping of the Law. Whenever we see the Kingdom in its beauty and fullness, there is a weakening, or even an unraveling of the Law of the Old.
Of course, He has us in the 21st century in His great mind and heart, but by no means does he "use" His compatriots as props. He is square with them, it is all true and all is real. They are not literature. They are life! They are of the Old Covenant, and treated thusly. We are "A.D". On this side of the New Covenant, and the cross. Much has happened, and the promise to Abraham that the Gentiles will be blessed has happened, and there is now one table, and one new reality - the Body of Christ.
This understanding of the New Covenant finally having come, and now standing in the stead of the Old Covenant, making the old obsolete, is found in the Epistle to the Hebrews, a letter to the Church, perhaps in Alexandria Egypt which was a church largely made up of Jews. Here the first covenant is being spoken of, and then the New Covenant coming after: Hebrews 8: 7-13 - "For if the first covenant had been faultless, then no place would have been sought for a second (then comes the quote from Jeremiah 31 about the New Covenant to come. Then...) In that He says, 'a New Covenant', He has made the first obsolete. Now what is becoming obsolete and growing old is ready to vanish away."
This interpretation of the above is true to the Greek and the Aramaic, and consistent with much of the Epistles of Paul when he speaks of the non-applicability of the Law for Christians - such as the Law being a school teacher to lead us to Christ whom having now found we have no need of the Law anymore. We are not "under the Law", etc. We can see, also, that in a profound way, there has been given us another Guide to fulfill the old purpose of the Torah, He is the Holy Spirit, which first came in fullness, by the way, on the day of the celebration in Judaism of the giving of the Law. This day is Shavuot (Pentecost in Greek). The Holy Spirit in and among us is very much a reality of Guidance and consolation, direction and strengthening, as the Law had been formerly.
One last note. We are accustomed to think in the categories of Chronology instead of the more Biblical ones. We look for a time and a date, at which the epoch or covenant ends and the new epoch and covenant commences. This fallacy underlies, for example, attempts to set an "age of accountability", and by doing so misunderstands and sets aside the biblical understanding of responsibility according to light and capability. But notice, "is becoming obsolete", "growing old","ready to vanish away". All this leave us with a profound and little appreciated thought - the old is in force to the extent, and wherever and when it is that the Kingdom with all its righteous might and power has not come or not come in fullness. And the old cannot stand and remain and survive, where ever and whenever it is that the Kingdom has come or is coming in all its power, as was evidenced in the life of the Lord Jesus Christ. We ought to see that and respect that in life and societies all around us and ought to be able to see that that is the reason for new and the good that is breaking through.
This is the true perspective in the era of the New Covenant, "Now what is becoming obsolete and growing old is ready to vanish away".