Trying to keep it simple...
The Mosaic Law was external and imperfect and is replaced for the believer by the 'Law of the Spirit' in our hearts.
This was predicted by Jeremiah in these two prophesies.
Jer 31
31“Behold, days are coming,” declares the LORD, “when I will make a new covenant with the house of Israel and with the house of Judah,
32not like the covenant which I made with their fathers in the day I took them by the hand to bring them out of the land of Egypt, My covenant which they broke, although I was a husband to them,” declares the LORD.
33“But this is the covenant which I will make with the house of Israel after those days,” declares the LORD, “I will put My law within them and on their heart I will write it; and I will be their God, and they shall be My people.
34“They will not teach again, each man his neighbor and each man his brother, saying, ‘Know the LORD,’ for they will all know Me, from the least of them to the greatest of them,” declares the LORD, “for I will forgive their iniquity, and their sin I will remember no more.”
Jer 32
38They shall be My people, and I will be their God;
39and I will give them one heart and one way, that they may fear Me always, for their own good and for
the good of their children after them.
40“I will make an everlasting covenant with them that I will not turn away from them, to do them good; and I will put the fear of Me in their hearts so that they will not turn away from Me.
41“I will rejoice over them to do them good and will faithfully plant them in this land with all My heart and with all My soul.
So we have a living law in our hearts that directs us to right action in all circumstances - something that the Mosaic Law never did.
Keeping to the Law of the Spirit requires our obedience and results in eternal rewards.
Breaking covenant is rendered impossible by the indwelling fear of Him.
The Law of the Spirit is referenced in Romans 8 as follows:
1Therefore there is now no condemnation for those who are in Christ Jesus.
2For the law of the Spirit of life in Christ Jesus has set you free from the law of sin and of death.
3For what the Law could not do, weak as it was through the flesh, God
did: sending His own Son in the likeness of sinful flesh and
as an offering for sin, He condemned sin in the flesh,
4so that the requirement of the Law might be fulfilled in us, who do not walk according to the flesh but according to the Spirit.