He changed what man had added to the Law, or what man reinterpreted of the Law.
The Law will be enforced perfectly, and judgment executed truthful and perfect, during the Millennium rein of The Messiah.
Unlike today under man's/satan's laws
He hasn't changed the essence of the law. The Mosaic Law of the Old Testament was written for the chosen people of Israel. Israel was chosen for a purpose—
Genesis 12:1-3. They were God’s instruments to accomplish a plan of rescue for the world: God becoming man as a member of the Jewish race and dying on the cross for man’s crimes against God. They were not chosen to be saved, rather they were chosen to be used to accomplish God’s plan of salvation. Many of those Jews took advantage of the mercy offered through that plan, and many went wayward. Israel’s being chosen did not secure their salvation. It secured a salvation plan for the world, and whether they individually participated in it or not was another question.
Christians are the chosen in the sense that those who are in Christ, putting their trust in Him, are the ones that benefited from that plan of salvation God was working out through Israel. We put our confidence in Him, so we are chosen regarding salvation.
God is the same yesterday, today, and forever. Jesus is the same yesterday, today, and forever because He is God. God doesn’t change, but that does not mean the way He deals with mankind doesn’t change. God dealt with Adam and Eve in one way, and He dealt with the Jews through Abraham with a different plan. He deals with Christians now through a new plan, a new covenant.
There was a unique relationship God had with the nation of Israel as part of the execution of that plan. There is a unique kind of plan that He has in the new covenant that's expressed through Jesus and what He did on the cross.
God changes a lot of different things. He can make plans and play things out so that certain things apply in some cases and don’t apply later, though His purpose is constant and unchanging.
The Mosaic Covenant is a treaty God made with the Jews, the nation of Israel. What was the point of the book of Deuteronomy? Deuteronomy is the second time the law is given. It is first given in Exodus when Moses is at Mount Sinai. There’s 40 years of wandering and the first generation dies away. Then there’s a new generation that takes the land under Joshua. Before Moses dies he gives that same law again a second time in Deuteronomy to the new generation that is now meant to take the land and live according to this law as a nation. The important thing is that this is an agreement that God made with Israel. It is not an agreement God made with anyone else.
Nothing that is in the Mosaic Law applies to me as a Gentile in virtue of it being in the Mosaic Law. No command is incumbent upon me in virtue of being part of the law.
The Mosaic covenant is like a state law. It was given to those people in that state for that period of time. We are in a different state now. We have a different covenant that applies to us—the new covenant with different obligations. We are not obliged by everything in the Mosaic Law. That was a set of civil obligations that were applicable to those people in that nation. It was made between God and Moses and Israel. God took them out of the land, He rescued them, and they were obligated to Him as their Sovereign. They had to keep the terms of the covenant. If they did, He would protect them, and if they didn’t, He would forsake them (Deuteronomy 28). There are blessings and curses in the Mosaic Covenant meant for Israel.
The Mosaic contract is no longer in force. It has been replaced for everyone, including Jews, by the new contract. The new contract is a new enterprise. Gentiles were never under the old contract. Now, Jews and Gentiles alike who put their faith in Jesus are under the new contract.
Does that mean we can go around murdering people because we’re not under the Mosaic Law? No. The obligation not to murder is universal and should be in any law. Just as our law does, the Mosaic Law included universal moral principles. So we are obligated to follow those moral rules, not in virtue of them being in the Mosaic law, but because they are universal for all people. The Mosaic law included universal moral rules and rules that were limited to the nation who lived under that contract. We have to distinguish between these as we consider how we relate to the Mosaic covenant now.