15 The Lord your God will raise up for you a prophet like me from among you, from your fellow Israelites. You must listen to him. (Deuteronomy 18)
Prophet like Moses is a unique prophet. He is like Moses because he is going to bring a law. A new one. That is one of the commandments given to Israel through Moses. It is part of the Torah. So Moses himself prophesied about the time when his law is going to be replaced with a new one.
Matthew through his gospel pictured Jesus as the new Moses. Story after story he shows that the life of Moses was a shadow of the Messiah. The sermon on the mount of Matthew 5 hyperlinks with the law of Sinai and signals the change.
As an example:
33 “Again, you have heard that it was said to the people long ago, ‘Do not break your oath, but fulfill to the Lord the vows you have made.’
34 But I tell you, do not swear an oath at all: either by heaven, for it is God’s throne;
35 or by the earth, for it is his footstool; or by Jerusalem, for it is the city of the Great King.
36 And do not swear by your head, for you cannot make even one hair white or black.
37 All you need to say is simply ‘Yes’ or ‘No’; anything beyond this comes from the evil one. (Matthew 5)
3 “When a young woman still living in her father’s household makes a vow to the Lord or obligates herself by a pledge
4 and her father hears about her vow or pledge but says nothing to her, then all her vows and every pledge by which she obligated herself will stand.
5 But if her father forbids her when he hears about it, none of her vows or the pledges by which she obligated herself will stand; the Lord will release her because her father has forbidden her.
6 “If she marries after she makes a vow or after her lips utter a rash promise by which she obligates herself
7 and her husband hears about it but says nothing to her, then her vows or the pledges by which she obligated herself will stand.
8 But if her husband forbids her when he hears about it, he nullifies the vow that obligates her or the rash promise by which she obligates herself, and the Lord will release her.
9 “Any vow or obligation taken by a widow or divorced woman will be binding on her.
10 “If a woman living with her husband makes a vow or obligates herself by a pledge under oath
11 and her husband hears about it but says nothing to her and does not forbid her, then all her vows or the pledges by which she obligated herself will stand.
12 But if her husband nullifies them when he hears about them, then none of the vows or pledges that came from her lips will stand. Her husband has nullified them, and the Lord will release her.
13 Her husband may confirm or nullify any vow she makes or any sworn pledge to deny herself.
14 But if her husband says nothing to her about it from day to day, then he confirms all her vows or the pledges binding on her. He confirms them by saying nothing to her when he hears about them.
15 If, however, he nullifies them some time after he hears about them, then he must bear the consequences of her wrongdoing.” (Numbers 30)
Father above is a picture of God. Woman is a picture of Israel who took a vow to keep the law of Moses (Exodus 19:8, 20:19 & 24:7-8). Husband is a picture of Christ that took the punishment for nullifying woman's vow. Since Jesus nullified that vow, He forbade His people from swearing new ones.
The second point is that if God wanted all the peoples to keep the Torah now, He wouldn't destroy the temple some forty years after the crucifixion. Since a massive chunk of the law relied on the temple services, it doesn't make any sense to claim that the law is still binding.
Even if the temple was standing, the laws requiring every believing man to travel three times a year to Jerusalem would be impossible. Besides, Jesus Himself told the Samaritan woman that it was going to change.
21 “Woman,” Jesus replied, “believe me, a time is coming when you will worship the Father neither on this mountain nor in Jerusalem.
22 You Samaritans worship what you do not know; we worship what we do know, for salvation is from the Jews.
23 Yet a time is coming and has now come when the true worshipers will worship the Father in the Spirit and in truth, for they are the kind of worshipers the Father seeks.
24 God is spirit, and his worshipers must worship in the Spirit and in truth.” (John 4)
As a shadow of the work of Jesus Christ, Joshua ben Nun (Jesus the son of the fish – another hyperlink this time also to the book of Johna) brings the second generation of the Israelites that was uncircumcised and free from the law of Moses (the Sinai vow wasn't binding on all younger than 20 years old, Numbers 14:28-31 & Deuteronomy 1:39) to the promised land (Joshua 3). They entered because of the faithfulness of their leader and Kaleb, who picture faithfulness of Christ. The Israelites were circumcised while already in the land (Jushua 5), and only there in Shechem („shoulder”) took upon themselves the yoke of the law (Joshua 8). Moses as a symbol of the law did not enter the land of the promise.
Notice also that the New Jerusalem is not built on Moses and the Torah, but on the good news of Jesus spread by the apostles:
14 The wall of the city had twelve foundations, and on them were the names of the twelve apostles of the Lamb. (Revelation 21)
Jesus is a descendant of David from the tribe of Judah. The law of Moses allowed only the priests from the tribes of Levy. That again proves that the law has been changed.
11 If perfection could have been attained through the Levitical priesthood—and indeed the law given to the people established that priesthood—why was there still need for another priest to come, one in the order of Melchizedek, not in the order of Aaron?
12 For when the priesthood is changed, the law must be changed also.
13 He of whom these things are said belonged to a different tribe, and no one from that tribe has ever served at the altar.
14 For it is clear that our Lord descended from Judah, and in regard to that tribe Moses said nothing about priests.
15 And what we have said is even more clear if another priest like Melchizedek appears,
16one who has become a priest not on the basis of a regulation as to his ancestry but on the basis of the power of an indestructible life.
17 For it is declared: “You are a priest forever, in the order of Melchizedek.”
18 The former regulation is set aside because it was weak and useless
19 (for the law made nothing perfect), and a better hope is introduced, by which we draw near to God.
20 And it was not without an oath! Others became priests without any oath,
21 but he became a priest with an oath when God said to him: “The Lord has sworn and will not change his mind: ‘You are a priest forever.’ ”
22 Because of this oath, Jesus has become the guarantor of a better covenant.
23 Now there have been many of those priests, since death prevented them from continuing in office;
24 but because Jesus lives forever, he has a permanent priesthood.
25 Therefore he is able to save completely those who come to God through him, because he always lives to intercede for them.
26 Such a high priest truly meets our need—one who is holy, blameless, pure, set apart from sinners, exalted above the heavens.
27 Unlike the other high priests, he does not need to offer sacrifices day after day, first for his own sins, and then for the sins of the people. He sacrificed for their sins once for all when he offered himself.
28 For the law appoints as high priests men in all their weakness; but the oath, which came after the law, appointed the Son, who has been made perfect forever. (Hebrews 7)
In Genesis 25 we read:
24 And when her days to be delivered were fulfilled, behold, there were twins in her womb.
Septuagint uses here the same Greek word for fulfil that Matthew in 5:17, πληρόω. The fulfilment of the pregnancy is the child. The fulfilment of the law is the Messiah.
Israel in the OT is called by God His treasured possession, His segulah. Segulah - feminine passive participle of an unused root meaning to shut up; wealth (as closely shut up) -- jewel, peculiar (treasure), proper good, special. So Israel until the coming of Christ was a shut up treasure. And the law of Moses was their protection. It was foreshadowed in the story of Noah. Just like Israel, Noah's family was protected from death (in his case literal not spiritual) by the ark, which is another picture of Jesus. After the flood, Noah made a sacrifice on the top of mount Ararat from clean animals and the wood of the ark (shadow of Christ's atonement). Because of the sacrifice, God promised to not bring another judgement on humanity, using the same arguments that inspired Him to bring the flood (shadow of Christ's atonement). God also said:
3 Every moving thing that liveth shall be meat for you; even as the green herb have I given you all things. (Genesis 9)
Which is a shadow of the importance of the kosher diet. It may be still important because of the health benefits, but it profits only the body. And that is the biggest change that the new covenant brought. Shift from the body to the spirit. The law of Moses dealt only with the physical body. And it is unredeemable. It has to be transformed.
50 I declare to you, brothers and sisters, that flesh and blood cannot inherit the kingdom of God, nor does the perishable inherit the imperishable.
51 Listen, I tell you a mystery: We will not all sleep, but we will all be changed—
52 in a flash, in the twinkling of an eye, at the last trumpet. For the trumpet will sound, the dead will be raised imperishable, and we will be changed.
53 For the perishable must clothe itself with the imperishable, and the mortal with immortality.
54 When the perishable has been clothed with the imperishable, and the mortal with immortality, then the saying that is written will come true: “Death has been swallowed up in victory.”
55 “Where, O death, is your victory?
Where, O death, is your sting?”
56 The sting of death is sin, and the power of sin is the law.
57 But thanks be to God! He gives us the victory through our Lord Jesus Christ. (1 Corinthians 15)
16 So from now on we regard no one from a worldly point of view. Though we once regarded Christ in this way, we do so no longer.
17 Therefore, if anyone is in Christ, the new creation has come: The old has gone, the new is here!
18 All this is from God, who reconciled us to himself through Christ and gave us the ministry of reconciliation:
19 that God was reconciling the world to himself in Christ, not counting people’s sins against them. And he has committed to us the message of reconciliation.
20 We are therefore Christ’s ambassadors, as though God were making his appeal through us. We implore you on Christ’s behalf: Be reconciled to God.
21 God made him who had no sin to be sin for us, so that in him we might become the righteousness of God. (2 Corinthans 5)
10 They are only a matter of food and drink and various ceremonial washings—external regulations applying until the time of the new order.
11 But when Christ came as high priest of the good things that are now already here, he went through the greater and more perfect tabernacle that is not made with human hands, that is to say, is not a part of this creation.
12 He did not enter by means of the blood of goats and calves; but he entered the Most Holy Place once for all by his own blood, thus obtaining eternal redemption.
13 The blood of goats and bulls and the ashes of a heifer sprinkled on those who are ceremonially unclean sanctify them so that they are outwardly clean.
14 How much more, then, will the blood of Christ, who through the eternal Spirit offered himself unblemished to God, cleanse our consciences from acts that lead to death, so that we may serve the living God! (Hebrews 9)
PS: Parallel to Matthew 5:17-20 is Luke 16:16-18.
16 “The Law and the Prophets were proclaimed until John. Since that time, the good news of the kingdom of God is being preached, and everyone is forcing their way into it.
17 It is easier for heaven and earth to disappear than for the least stroke of a pen to drop out of the Law.
18 “Anyone who divorces his wife and marries another woman commits adultery, and the man who marries a divorced woman commits adultery.
Paul explained in his Letter to Romans how Jesus freed us from the law using same marriage analogy:
1 Do you not know, brothers and sisters—for I am speaking to those who know the law—that the law has authority over someone only as long as that person lives?
2 For example, by law a married woman is bound to her husband as long as he is alive, but if her husband dies, she is released from the law that binds her to him.
3 So then, if she has sexual relations with another man while her husband is still alive, she is called an adulteress. But if her husband dies, she is released from that law and is not an adulteress if she marries another man.
4 So, my brothers and sisters, you also died to the law through the body of Christ, that you might belong to another, to him who was raised from the dead, in order that we might bear fruit for God.
5 For when we were in the realm of the flesh, the sinful passions aroused by the law were at work in us, so that we bore fruit for death.
6 But now, by dying to what once bound us, we have been released from the law so that we serve in the new way of the Spirit, and not in the old way of the written code. (Romans 7)
No man can keep the law perfectly. And the law is the standard of God's righteousness. So you can't become righteous in the eyes of God through your own works. You can only do it through faith in what Jesus' fulfilled.
21 But now apart from the law the righteousness of God has been made known, to which the Law and the Prophets testify.
22 This righteousness is given through faith in Jesus Christ to all who believe. There is no difference between Jew and Gentile,
23 for all have sinned and fall short of the glory of God,
24 and all are justified freely by his grace through the redemption that came by Christ Jesus.
25 God presented him as the mercy seat by his blood, through faith, to demonstrate his righteousness, because in his restraint God passed over the sins previously committed.
26 he did it to demonstrate his righteousness at the present time, so as to be just and the one who justifies those who have faith in Jesus. (Romans 3)
Since we collectively are the body of Christ, Jesus cleanses and sanctifies us, because He is the head of that body.
1 As for you, you were dead in your transgressions and sins,
2 in which you used to live when you followed the ways of this world and of the ruler of the kingdom of the air, the spirit who is now at work in those who are disobedient.
3 All of us also lived among them at one time, gratifying the cravings of our flesh and following its desires and thoughts. Like the rest, we were by nature deserving of wrath.
4 But because of his great love for us, God, who is rich in mercy,
5 made us alive with Christ even when we were dead in transgressions—it is by grace you have been saved.
6 And God raised us up with Christ and seated us with him in the heavenly realms in Christ Jesus,
7 in order that in the coming ages he might show the incomparable riches of his grace, expressed in his kindness to us in Christ Jesus.
8 For it is by grace you have been saved, through faith—and this is not from yourselves, it is the gift of God—
9 not by works, so that no one can boast.
10 For we are God’s handiwork, created in Christ Jesus to do good works, which God prepared in advance for us to do.
11 Therefore, remember that formerly you who are Gentiles by birth and called “uncircumcised” by those who call themselves “the circumcision” (which is done in the body by human hands)
12 remember that at that time you were separate from Christ, excluded from citizenship in Israel and foreigners to the covenants of the promise, without hope and without God in the world.
13 But now in Christ Jesus you who once were far away have been brought near by the blood of Christ.
14 For he himself is our peace, who has made the two groups one and has destroyed the barrier, the dividing wall of hostility,
15 by setting aside in his flesh the law with its commands and regulations. His purpose was to create in himself one new humanity out of the two, thus making peace,
16 and in one body to reconcile both of them to God through the cross, by which he put to death their hostility.
17 He came and preached peace to you who were far away and peace to those who were near.
18 For through him we both have access to the Father by one Spirit.
19 Consequently, you are no longer foreigners and strangers, but fellow citizens with God’s people and also members of his household,
20 built on the foundation of the apostles and prophets, with Christ Jesus himself as the chief cornerstone.
21In him the whole building is joined together and rises to become a holy temple in the Lord.
22 And in him you too are being built together to become a dwelling in which God lives by his Spirit. (Ephesians 2)
15 The Son is the image of the invisible God, the firstborn over all creation.
16 For in him all things were created: things in heaven and on earth, visible and invisible, whether thrones or powers or rulers or authorities; all things have been created through him and for him.
17 He is before all things, and in him all things hold together.
18 And he is the head of the body, the church; he is the beginning and the firstborn from among the dead, so that in everything he might have the supremacy.
19 For God was pleased to have all his fullness dwell in him,
20 and through him to reconcile to himself all things, whether things on earth or things in heaven, by making peace through his blood, shed on the cross.
21 Once you were alienated from God and were enemies in your minds because of your evil behavior.
22 But now he has reconciled you by Christ’s physical body through death to present you holy in his sight, without blemish and free from accusation—
23 if you continue in your faith, established and firm, and do not move from the hope held out in the gospel. This is the gospel that you heard and that has been proclaimed to every creature under heaven, and of which I, Paul, have become a servant. (Collosians 1)
17 But whoever is united with the Lord is one with him in spirit. (1 Corinthians 6)