Matthew 5:17-20 (KJV)
Think not that I am come to destroy the law, or the prophets: I am not come to destroy, but to fulfil.
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.
For I say unto you, That except your righteousness shall exceed the righteousness of the scribes and Pharisees, ye shall in no case enter into the kingdom of heaven.
Like many Christians I read and reread this section of Scripture without really understanding what it was saying. The words themselves are relatively simple, yet because of translation issues and historical theology, the plain meaning of the text has been lost to the majority of Christians today.
Yeshua sat on a hill with his disciples around Him (Matthew 5:1). He began to teach starting with the Beatitudes (Matthew 5:3-12). Then He spoke about believers being salt to the Jews and light to the Gentiles (see http://eclecticchristian.blogspot.com/2015/05/salt-and-light.html) Next He told His listeners that they were not to think that He had come to destroy the Torah or the Prophets (the whole Word of God), but that He had come to fulfill them (verse 17). The religious leaders of Yeshua's day constantly accused Yeshua of violating the Torah of God, but if that were really the case and Yeshua had actually violated a single commandment of the Torah, Yeshua would not have been sinless and would not have been qualified to die on mankind's behalf. There would be no salvation nor eternal life for anyone!! What Yeshua objected to was the religious leaders' misinterpretation of the Torah and their elevating the Oral Law to the status of the Word of God. Yeshua was guilty only of violating the man made rules that the religious leaders had, that often conflicted with the Torah.
To strengthen His statement, Yeshua declared that the Torah would not pass away until heaven and earth passed away (verse 18). Since heaven and earth are obviously still present, the Torah cannot have been done away with. However, the last part of verse 18 seems to imply that the Torah would pass away when it was all fulfilled. The conclusion by many is that despite the continued presence of heaven and earth, Yeshua fulfilled the Torah and it has passed away. Logically, this conclusion doesn't make any sense, especially when verse 19 is read. According to traditional Christianity Yeshua fulfilled the Torah, so that believers now are free to worship on Sunday instead of Saturday, ham is permissible as food, and the holy days like Passover and Yom Kippur can be ignored. Yet, verse 19 says that anyone who breaks one of the least commandments or teaches men so will be called the least in the Kingdom of Heaven. Obviously, the breaking of the Sabbath, food laws, and Holy Days comes with a stiff penalty.
The problem in this section that has led to much misunderstanding is the word fulfill, which is used to translate two different Greek words. In the first occurrence in verse 17, the Greek word behind fulfill is pleroo. This word means "to fill to the full" or "to complete." Therefore, Yeshua completed (or did) (or obeyed) the Torah and showed mankind how to do likewise. The second Greek word that is translated as fulfill in verse 18 is the word ginomai, which means "to occur" or "to happen." In other words the Torah would not pass away until everything (meaning the whole of history stated in Scripture - Genesis to Revelation) had happened.
I have heard commentators try to get around the sensible meaning of this text by saying that verses 17 and 18 refer to the ritual laws, that Yeshua fulfilled them and that they are done away with. Then verses 19 and 20 refer to the moral law, that these should not be violated. However, in verse 19 the word "therefore" connects verse 19 to verse 18 and there is no hint that the subject of the sentence had changed. Also, there is no place in Scripture where God's commands are divided into ritual versus moral law. This is a man made construct that isn't Biblically based.
The religious leaders of Yeshua's day were accusing Yeshua of destroying the Torah. Let's not do the same thing today by saying that the Torah has been fulfilled and has passed away.