Matthew 5:17 - Don't think that I came to destroy the law or the prophets. I didn't come to destroy, but to fulfill.
Matthew 5:18 - For most assuredly, I tell you, until heaven and earth pass away, not even one smallest letter or one tiny pen stroke shall in any way pass away from the law, until all things are accomplished.
Many do not realize that these words of Jesus were spoken to and concerning those "under the Law." Some have sought to use the above words to bind Gentiles to the Law Covenant; however, this is not what Jesus was talking about. Jesus also stated: "The law and the prophets were until John." (Luke 16:16) John wrote: "For the law was given through Moses. Grace and truth came through Jesus Christ.." (John 1:17) And Jesus stated: "Everyone who divorces his wife, and marries another, commits adultery. He who marries one who is put away from a husband commits adultery." Jesus was here speaking the covenant to which the children of Israel are bound. The children of Israel cannot become divorced from the Law, so as to belong to another, without symbolically committing adultery (unfaithfulness). Jesus cannot become the Lord of one who belongs to the Law without also symbolically committing adultery (unfaithfulness). Jesus continues in Luke 16 to describe in the parable of the rich man and Lazarus the separation between the Law Covenant and the Covenant of Grace.
Paul asks: "Don't you know, brothers (for I speak to men who know the law), that the law has dominion over a man for as long as he lives?" -- Romans 7:1.
It is the sons of Israel (not the Gentiles) who are bound to the Law Covenant. That Law Covenant was not given to any other nation but the nation of Israel. The everlasting law covenant with Israel was still upon the Jew in general when Jesus gave his sermon on the mount, and it is still in effect to those still under the law, although it can not give life to anyone due to the sinful flesh. "For as many as are of the works of the law are under a curse." -- Galatians 3:10.
The law covenant is never destroyed, but it does "pass away," 'vanish,' (Hebrews 8:11), once all of its subjects have died, either actually or reckonedly. "The law has dominion over a man for as long as he lives." (Romans 7:1) "Now we have been discharged from the law, having died [reckonedly -- Romans 6:11] to that in which we were held." -- Romans 7:6.
The Law Covenant was designed only for man in his sinful state; it was not designed for the righteous, the justified. (1 Timothy 1:9) If one under the law could fully obey that Law, one could have been justified by such obedience, and such a person would have eternal life by the Law. None of Adam's descendants were so justified by means of Law, for, due to the weakness of sinful flesh, no one could be fully obedient to that Law.
Furthermore, the Law Covenant was not given to all mankind, but only to the nation of Israel. --Exodus 19:5; Deuteronomy 7:6; Amos 3:2.
Gentiles who are grafted into the ecclesia of Christ (Romans 11:17-24) as the seed of Abraham (Galatians 3:15-18) are not grafted into the law covenant, as many assume, for if they were, it would only serve to be a curse for them. (Galatians 3:10) It would further mean that they had not been justified (declared righteous), since it would still account them as sinners. -- 1 Timothy 1:9.
Nevertheless, Jesus, as the seed of promise (Genesis 3:15; Isaiah 9:6,7), the promised son of the man, David (Acts 13:23), had already begun to use his authority as the promised son of David to magnify the Law.
Jesus' purpose was not to destroy the law, but to fulfill and establish the justness of the Law, which, as a human being (Hebrews 2:9) while in days of his flesh (Hebrews 5:7), did by his full obedience to the Law. On the other hand, the covenant with Abraham and his seed had already been confirmed long before the Law Covenant. -- Galatians 3:16,17.
In many cases, however, it is as the "seed of Abraham" that Jesus acts. Jesus, of course, having received a body especially prepared by his God and Father (Hebrews 10:5; John 6:33,51), did not have the condemnation of Adam, as the rest of mankind. (Romans 5:12-19; 1 Corinthians 15:21,22) And yet, he, although not a sinner was born under the law. (Galatian 4:4) How could he, a righteous man, be under the law, when the law was made for sinners? The prophet wrote that "Jehovah has laid on him the iniquity of us all." (Isaiah 53:6) This, of course, was in a reckoned manner, not because Jesus' flesh was actually sinful. Jesus came into the world of mankind in the "likeness" [not actually] of sinful flesh (Romans 8:3) only because Jehovah had laid upon him the iniquity of the whole world. He suffered and died as though he were a sinner, although in reality he wasn't. And yet, through his obedience, Jesus condemned sin the flesh (Romans 8:3) and fulfilled the commandments of the Law.
The fulfilling of the law, however, requires not just the keeping of the law commandments, but also the fulfilling of the typical arrangements provided in the law by the realities that are pictured by those types. Many of these types involve the Church of Christ, and thus, the fulfilling of the law extends beyond Jesus himself. (Colossians 2:17; 8:5; 10:1) Since some of these typical arrangements are not fulfilled until the age to come, then the present heaven and earth must pass away before the law is totally fulfilled. Furthermore, the entire Law is still active upon all who are under that Law. For those under the Law, nothing at all in the Law passes away until after the present heavens and earth pass away. -- Matthew 5:18; Luke 16:17
Nevertheless, Jesus had to be born under the law, and to suffer as though he were disobedient to that law, else he could not have purchased, redeemed any from the curse of the law. -- Galatians 3:13.
Romans 4:13 - For not through the law was the promise to Abraham or to his seed that he should be heir of the world, but through the righteousness of faith.
Romans 4:14 For if those who are of the law are heirs, faith is made void, and the promise is made of no effect.
Jesus' inheritance was not of the law covenant (Galatians 3:18; Romans 4:13), although Jesus, being born under the Law (Galatians 4:4), was obligated to keep the Law covenant (Romans 3:19; James 2:10; Romans 7:1), which he did perfectly, else he would have been cursed under the Law just as the Jews in general. (Galatians 3:10) If he had failed in one small matter (James 2:10), he would not have received the inheritance, since he would be condemned just as everyone else under the law. While his keeping the law perfectly proved him to be the promised one, his inheritance as the promised one was due to his being the seed of Abraham, the seed of David, not due the law covenant itself. Likewise, the believers' inheritance is because -- through faith in Jesus -- they are made the seed of Abraham with Jesus, and it is not attributed to the law covenant, nor is it directly attributable to the new covenant, but we do believe one has be first become a son by appropriating the blood of the new covenant before he can become members of the seed of Abraham. (Matthew 26:28; Mark 14:24; Luke 22:20; 1 Corinthians 11:25; Hebrews 10:29; 12:24) Hebrews 10:29 shows, also, that new creature in Christ must stay under the blood of the new covenant, or else one can be subject a condemnation for which no sacrifice is provided. -- Hebrews 10:26.
And yet we should realize that the new covenant does not have its actual "beginning" until the age to come, when God, by means of that covenant releases the dead from the tomb through application of the blood of Christ. There could be no resurrection of either the just or the unjust without an application of the blood of the new covenant that releases the dead so that they may be raised in the last day, whether to life or judgment. Nevertheless, the believers in this age receive the application of the new covenant through the holy spirit as a token, a down payment, an earnest, of the reality to follow. (2 Corinthians 1:21,22; 5:4,5; Ephesians 1:13,14) They, in effect, taste of powers of the age to come. (Hebrews 6:5) Being transferred thereby into the coming kingdom (Colossians 1:13), they become representatives of that kingdom in the midst of corrupt generation (Philippians 2:15), and servants of a new covenant. -- 2 Corinthians 3:6.
The new covenant, however, is not just for the purpose of releasing the dead from the death condition resulting from Adam, but it is also for the purpose of reconciliation (Romans 5:11; 2 Corinthians 5:19), returning mankind not only to what Adam had before Adam sinned, but also returning mankind to the possibility of perfecting love and faith in the Creator, as Adam could have done. This, of course, does not mean that any released from the condemnation in Adam becomes lawless. Through Christ's obedience to God, including his obedience to the law covenant, as a man, and due to his proving himself unswervingly incorruptible as a man, he brought life and incorruption to light. (1 Corinthians 15:54; 2 Timothy 1:10) A sinless man had not only kept God's law, but had also proven himself to to be *incorruptible* in obedience to his God and Father.
It is true that the until the apostles were enlightened by the holy spirit there was no general understanding of the basis of salvation. God, however, who calls things that are not as though they were (Romans 4:17), could and did bring a reckoning of salvation before the sacrifice of Jesus was made, since God had foreknowledge that the sacrifice was to be given, and thus due to his foreknowledge, that which was not yet was reckoned as being as though it had already happened, just as he counts people as alive in view of the coming resurrection in the last day. -- Luke 20:37,38
Question: Are you saying that we have to abide by OT law?
No; that Law was only with the nation of Israel (Exodus 19:5; Deuteronomy 7:6; Amos 3:2), and as each member of that nation accepts Jesus or actually dies, that law is no longer in effect for that person, and thus that person is no longer condemned by that law. -- Romans 7:1-4; Galatians 3:10.