There is a major misconception called antinomianism and some people think that Jesus abolished the law when he fulfilled it, while in reality he abolished the punishment for disobeying the law, not the law itself. First let's look at the usage of fulfill that is commonly used in mainstream Christianity. They pretty much claim that fulfill means to end. So in Matthew 5:17-18, they're saying Jesus ended the Law. Using the same logic, they must also agree that in Matthew 3:15, Jesus abolished/ended righteousness when he got baptized. And likewise for Romans 13:8 that when we love, we are ending the law.
Fulfill simply means to do something that is expected, hoped for, or promised. So when we are loving others, as the law commands, we are completing its expectations/requirements.
Jesus fulfilling the law means we are not under the punishment of the law like the people were in the old testament. We are saved by grace through faith alone, but the law was never abolished and it still pleases God when you obey all of his commandments. While we are saved by grace, we are still rewarded for following God's law and other good works that we do. Jesus said in Matthew 5:19 that those who ignore the least of God’s laws and teach others to do so will be the least in the kingdom of heaven, while those who obey the least of God’s laws and teach others to do so will be great in heaven. Acts 15:29 even gives us some old testament laws for new Christians to follow as a minimum, but people continue to ignore the rest of the law even after they are no longer new Christians. They continue to misinterpret Paul's teaching as if the law doesn't exist anymore.
The law still determines what sin is, and the law is eternal.
1 John 3:4 “Whoever commits sin also commits lawlessness, and sin is lawlessness.”
Romans 7:7 “What shall we say then? Is the law sin? Certainly not! On the contrary, I would not have known sin except through the law. For I would not have known covetousness unless the law had said, “You shall not covet.”
Psalm 119:160 “The entirety of Your word is truth, And every one of Your righteous judgments endures forever.”
In Matthew 5:18 Jesus said that not a single letter will disappear from the law, meaning either ALL of the law is still valid, or NONE of it is. Obviously, all of it is still valid. Jesus never differentiated between moral, sacrificial, and other laws, they were all referred to as “the law”. We are not living in the nation of ancient Israel so civil laws do not apply to us, and we are told in Romans 13 to obey the authority of whatever nation we live in. As far as other OT laws like the animal sacrifices, we don't have the temple today, but we will in the future, and during the millennium rule of Christ the sacrifices will resume. Animal sacrifices will not be as an atonement for sins, but rather as remembrance or as a lesson that the wages of sin is death. Other laws such as Sabbath keeping, clean diet, keeping feasts, wearing tzitzit and other commandments still apply to us today.
https://www.gotquestions.org/millennial-sacrifices.html
Long before the law was given to Moses, Cain’s brother Able knew it was right to sacrifice animals to God, and Cain knew that fruits of his labor are not a valid sacrifice. Cain also knew that murder is wrong. God's law doesn't change.
People are confused about verses like Colossians 2:16 seemingly telling people not to worry about keeping the Sabbath or dietary laws, but in reality if you look at the context, Paul is speaking to new Christians who were among pagans that were judging them for not worshiping their false gods and instead keeping the Jewish feasts. Paul was telling them "don't let THEM judge you FOR keeping the Sabbath". This is just one of many misunderstood verses that people are confused about.
This rebellious antinomianism began with the 2nd century church leaders, somewhere between Clement of Rome, who defended the law, and Justin Martyr about 100 years later. The church leaders became antisemitic and started referring to Jews as Christ killers, and preached replacement theology that God has abandoned Jews in favor of gentiles. They said God’s commandments were given to Jews as “punishment”.
Clements letter to the Corinthians (Clement was a gentile successor of Paul.)
"These things therefore being manifest to us, and since we look into the depths of the divine knowledge, it behoves us to do all things in [their proper] order, which the Lord has commanded us to perform at stated times.[1] He has enjoined offerings [to be presented] and service to be performed [to Him], and that not thoughtlessly or irregularly, but at the appointed times and hours. Where and by whom He desires these things to be done, He Himself has fixed by His own supreme will, in order that all things, being piously done according to His good pleasure, may be acceptable unto Him.[2] Those, therefore, who present their offerings at the appointed times, are accepted and blessed; for inasmuch as they follow the laws of the Lord, they sin not. For his own peculiar services are assigned to the high priest, and their own proper place is prescribed to the priests, and their own special ministrations devolve on the Levites. The layman is bound by the laws that pertain to laymen.
Let every one of you, brethren, give thanks[1] to God in his own order, living in all good conscience, with becoming gravity, and not going beyond the rule of the ministry prescribed to him. Not in every place, brethren, are the daily sacrifices offered, or the peace-offerings, or the sin-offerings and the trespass-offerings, but in Jerusalem only. And even there they are not offered in any place, but only at the altar before the temple, that which is offered being first carefully examined by the high priest and the ministers already mentioned. Those, therefore, who do anything beyond that which is agreeable to His will, are punished with death. Ye see,[2] brethren, that the greater the knowledge that has been vouchsafed to us, the greater also is the danger to which we are exposed."
Ante Nicene fathers volume 9 chapter 40-41.
