I was raised in many denominations and every single one referred to the "Law" in this passage as either the Ten Commandments and/or the ceremonial laws for salvation. Even as knowledge is increasing about the true meaning of "Law" in the statement by Y'shua, most churches talk about how the Old Testament is gone in some way. One common statement is that the Old Testament is gone accept where it's repeated in the New Testament. (Read more about the Old and New Testament and their history)
One problem with these beliefs is that this passage is always pulled from its context. If we continue to read we see "Whoever therefore breaks one of the least of these commandments, and teaches men so, shall be called least in the kingdom of heaven; but whoever does and teaches them, he shall be called great in the kingdom of heaven." (Matthew 5:19)
The most common argument I've heard on verse 19 is that it doesn't say you don't get to go, it just says you're "least in the kingdom of heaven". Not to beat up on these individuals but can we think with logic for a moment? If keeping these commandments and teaching to keep them makes a person great and not keeping these commandment and teaches men not to keep them makes one least what does that tell us about the importance of "these commandments" which is referring back to the "Law" statement? It actually tells us they still exist and it's not good to break them.
This takes us back to the common teaching of "fulfill". The most common teaching of Y'shua's statement of I come to "fulfill" is that He did away with them in His coming. Again, a little logic please.
The definition of "fulfill" is to "bring to completion or reality; achieve or realize".
The definition of "destroy" is "put an end to the existence of"
In efforts to rid ourselves from the "Evil mean God of the Jews" who was just full of rules no one could keep, and to bring ourselves out of as many rules as possible, man has disregarded the full definition of "fulfill", disregarded the context of the text, and caused a very confusing statement. They place fulfill in the category of "ending" something and use this very statement to support that the Law is ended. Let's look at the statement based upon modern teaching and the popular definitions.
"I did not come to [put an end to the existence of] but to [complete (end)]".
Now that makes no sense at all.
The first thing that needs to be established is what Y'shua is talking about here… "Law and Prophets". Whenever you see "Law" followed by "Prophets" you would get a better understanding of the subject by replacing "Law" with "Torah". The original text is "Torah and Prophets" which is to say the first five books of the Bible and the books of the Prophets.
Many words have different meanings which makes the meaning dependent upon the context of the statement or event. That rule needs to be applied here.
Since Y'shua already said He did not come to "destroy the Torah or the Prophets" then it's already been established that He's not ending them. Therefore, the definition "bring to completion" cannot be applied. This means He must be bringing to "reality" and "achieving" the Torah and Prophets. What would this mean and how does it look.
We need to always be looking at purpose when studying Scripture and God's desires for our lives and how we should walk. The Bible starts with Genesis 1 in God created man in His own image. A couple chapters later we see that man fell from that image by deciding to do things on their own terms. What follows is a history telling of God bringing man back to the original design - a man walking in His image. This is the purpose of the Torah and Prophets:
“‘You shall love the LORD your God with all your heart, with all your soul, and with all your mind.’ 38 This is the first and great commandment. 39 And the second is like it: You shall love your neighbor as yourself.’ 40 On these two commandments hang all the Law and the Prophets.” (Matthew 22:37-40)
When we see that Y'shua did not come to destroy but to establish or bring to realization the Torah and Prophets, and we understand that God established those books to bring us back into His image, it better clarifies where Y'shua then became the "second Adam" (Romans 5:12-21; 1 Corinthians 15:22, 44-49). He established within mans flesh, He revealed to us, the following of Torah and Prophets so that we too can walk in them. It IS IMPOSSIBLE to escape sin but it's NOT impossible to strive to walk like Y'shua walked. If it were, we would not be told to do so.
Now by this we know that we know Him, if we keep His commandments. 4 He who says, “I know Him,” and does not keep His commandments, is a liar, and the truth is not in him. 5 But whoever keeps His word, truly the love of God is perfected in him. By this we know that we are in Him. 6 He who says he abides in Him ought himself also to walk just as He walked. (1 John 2:3-6)
The Torah is not gone. In fact, while we are not under the covenant of Moses, we ARE under the Covenant of Abraham; it's not "New" its "Renewed".
Don't get hung up on building a rail around your roof (Deuteronomy 22:8), instead, look for the purpose. Understand that they were able to go up and lounge on their roofs and God wanted us to be mindful of our guest and protect them. I see this purpose and then make sure I keep my porch well maintained, clean up after my dogs, and such before any guest comes to my house. I do this because I should love my neighbor as myself.
Some of these purposes we will not understand, and that's ok, there's grace, but we need to understand that the two great commands are summed up in Love the Lord your God and love your neighbor. Summed up is a summary of something else and that something else is the Torah and Prophets where it's spelled out for us on HOW we accomplish the great command.