This has puzzled me ever since i became a christian. When i started reading the bible on my own and i read this in matthew how i thought it was: "Yup, we gotta keep the old testament law still, clearly"
And then I had the idea driven into me that this was still old covenant since Jesus hadnt died yet and its for the jews and all this.
But in my own mind it is FOREVER saying we should keep the law, but I still dont keep the law and sometimes i feel bad for it, and i think that because nobody else keeps it either i just misunderstood that passage.
I dunno, i havent heard any credible explanations to this, its always the love God and love your neighbor explanation, but wait a minute now, thats what the law of the OT tells us to do and how the 10 commandments are split forexample.
If anyone has a good explanation for how we dont need to keep the law, im all ears.
Notice that the verses say that NOT ONE JOT OR TITTLE WILL PASS FROM THE LAW UNTIL ALL IS FULFILLED.
We KNOW that animal sacrifices and the Levitical priesthood have "passed" from the Law, so if this verse was meant to prove the continued applicability of the Mosaic Covenant/Law, those who claim this have some explaining to do, as "jots and tittles" have passed from the Law if their interpretation of the verse is correct.
Additionally, Law and Prophets refers to the Old Testament in general, and not to the Mosaic Covenant in particular.
Read Acts 15, II Corinthians 3, Galatians 3-4, Ephesians 2:13-15, Romans 7:1-6, and Hebrews 7-8. "Torah observers" will try to import a false context into these verses, such as claiming they refer to the Oral Law or the "traditions of the elders" but those interpretations weren't binding to start with. Those who hold a given paradigm will often come up with false contexts, etcetera, to continue to justify their position.
I was a Sabbath/festival observer for over a decade. I can tell you that there is a STRONG TENDENCY amongst such individuals to be cultic...believing conspiracy theories about the Roman Catholic Church, Constantine, etcetera, which are not true and don't line up with church history. Also, they tend to be cliquish and talk about how they are so glad they learned "the truth", referring to their peculiar doctrines. They often separate themselves from the rest of Christianity, as they claim that the observances of days and meats make a crucial difference to God. Some simply claim others are in sin, others claim that they haven't met the requirement or condition of salvation and are unbelievers. When I was a Judaizer, I claimed others were not believers due to their non-observance of the Sabbath, festivals and clean meat laws. So do many other Judaizers.
On the other hand, there are SOME who don't make such claims. Jews for Jesus, for example, does not make such claims. They observe days and meats to remain connected to their Jewish heritage. Some Gentile believers appreciate the shadows and types of the Mosaic Covenant, and observe them as a result. I have no issue with such people, and they are not Judaizers. Judaizers reveal themselves eventually by their accusations, although often they speak in guarded manner in order to hide their true beliefs and contempt for non-observers.
I like this group called JerusalemAssembly on YouTube. They are balanced in this regard. They are Messianic Jews in Jerusalem. Meno Kalisher is their pastor. He's not a nut like I described above.
https://www.youtube.com/channel/UCbqxHKojvlUWBzFtUapcM5A
I would have no problem hanging out with these guys, but I would not recommend hanging out with nuts. Many of them also deny the Trinity, the full deity of Jesus, the writings of Paul, and follow the Mishnah and other non-inspired writings.
Here's a thread I did on Matthew 5:17-19 if you're interested:
http://christianchat.com/bible-discussion-forum/115415-matthew-5-17-19-sabbathkeeping-claims.html
I'd also highly recommend the book "Freedom in Christ" by Meno Kalisher. It is basically a commentary on Galatians. Not only does it cover Galatians well, it covers foundational truths of Christianity and how to rightly view the Mosaic Covenant in relation to the New Covenant. He has dealt with Judaizers over the course of his ministry, and is a fully committed evangelical Christian who observes the Sabbath and festival days without judging others. The message of Galatians is excellent with regards to refuting the claims of Judaizers.