Let's assume that Law, an agreement, is meant for all God's people, the Covenanted, whether Jew or Christian.
Let's also understand that the Law was given only on Israel's request:
Deuteronomy 5:25 But now, why should we die? This great fire will consume us, and we will die if we hear the voice of the Lord our God any longer. 26 For what mortal has ever heard the voice of the living God speaking out of fire, as we have, and survived? 27 Go near and listen to all that the Lord our God says. Then tell us whatever the Lord our God tells you. We will listen and obey.”
Although God did not want the law, He allowed it to be given, because it helped His future followers to identify Messiah.
Romans 3:1 Then what advantage has the Jew? Or what is the benefit of circumcision? 2 Great in every respect. First of all, that they were entrusted with the oracles of God.
Jeremiah 7:22 “For I did not speak to your fathers, or command them in the day that I brought them out of the land of Egypt, concerning burnt offerings and sacrifices. 23 “But this is what I commanded them, saying, ‘Obey My voice, and I will be your God, and you will be My people; and you will walk in all the way which I command you, that it may be well with you.’
It also would be used to make Israel a vessel of dishonour, so that Gentiles could be included in the Covenant:
Galatians 3: For as many as are of the works of the Law are under a curse; for it is written, "CURSED IS EVERYONE WHO DOES NOT ABIDE BY ALL THINGS WRITTEN IN THE BOOK OF THE LAW, TO PERFORM THEM."
Circumcision, symbolizing the cut animal that Abraham walked through, was followed to teach that the penalty for non performance of the Old Contract would be paid by Messiah:
Galatians 3:13 Christ redeemed us from the curse of the Law, having become a curse for us-- for it is written, "CURSED IS EVERYONE WHO HANGS ON A TREE "--
Thereby ending the Old Contract. Fulfilment of contracts can be either by delivering the promised service or by paying the penalty for non performance. The Covenanted People of God could now receive a new contract, with new terms and conditions.
There was no curse, because instead of Wrath, which the Old Covenant Law brought, there was Grace.
The Old Covenant requirement meant being oracle bearers, hired hands employed to pre-pubilicise the identity of Messiah, with obligations and receiving wages, protection from God's wrath. Law also meant non performance of ALL terms and conditions resulted in curse, penalty.
Grace only required faith, loyal response, from family members, in relationship. There was no letter of a contract, only the spirit of the relationship, to be followed. If we confessed non performance we could escape judgment. Confession, admission of guilt, was a loyal response:
1 John 1:9 If we confess our sins, He is faithful and righteous to forgive us our sins and to cleanse us from all unrighteousness.
In fact it was required, demonstrating honesty, humility and our constant need for God:
1 John 1:10 If we say that we have not sinned, we make Him a liar and His word is not in us.
Confession made us recipients of Grace, which made us compliant, and qualified to be blessings to the world:
2 Corinthians 12:9 And He has said to me, "My grace is sufficient for you, for power is perfected in weakness." Most gladly, therefore, I will rather boast about my weaknesses, so that the power of Christ may dwell in me.
Christians trying to observe the Old Covenant are saying with their actions that the Messiah has not been sent. Circumcision means the Redemption has not occurred, Sabbath keeping means our Rest is not available for entering, observing dietary restrictions meaning God's People are identified by what goes into the mouth, when Messiah proclaimed it was what came out of the mouth, and the heart, that separated them from unbelievers.
Abrogation was not new or exclusive to Jesus. He was only quoting a predecessor, who had long ago identified what summarized Law:
Hillel said to him, “What is hateful to you, do not to your neighbor: that is the whole Torah; the rest is commentary; go and learn it.”
Leviticus 19:18 You shall not take vengeance, nor bear any grudge against the sons of your people, but you shall love your neighbor as yourself; I am the LORD.
All Scripture from the NASB