The Curse of Breaking Even One Law
Under the Curse
Galatians 3:10-12 CSB
For all who rely on the works of the law are under a curse, because it is written, Everyone who does not do everything written in the book of the law is cursed.  Now it is clear that no one is justified before God by the law, because the righteous will live by faith.  But the law is not based on faith; instead, the one who does these things will live by them.
This is a direct reference to ALL the Commandments from the Book of the Law of Moses which includes the Ten Commandments.
Deuteronomy 27:26 CSB
‘Anyone who does not put the words of this law into practice is cursed.’ And all the people will say, ‘Amen!’
And, another direct reference to ALL the commandments of the Book of the Law of Moses. Galatians 3:12 directly quotes this verse.
Leviticus 18:4-5 CSB
You are to practice my ordinances and you are to keep my statutes by following them; I am the LORD your God.  Keep my statutes and ordinances; a person will live if he does them. I am the LORD.
Keep All the Law or Break Them All
You can’t just DO some of the laws. You must do ALL of them to have eternal life.
James 2:10 CSB
For whoever keeps the entire law, and yet stumbles at one point, is guilty of breaking it all.
Plus, everything written in the Book of the Law of Moses cannot be added to or subtracted from. Again, Galatians 3:19 referring to Deuteronomy 4:1
Deuteronomy 4:1-2 CSB
Now, Israel, listen to the statutes and ordinances I am teaching you to follow, so that you may live, enter, and take possession of the land the LORD, the God of your ancestors, is giving you.  You must not add anything to what I command you or take anything away from it, so that you may keep the commands of the LORD your God I am giving you.
Deuteronomy 12:32 CSB
Be careful to do everything I command you; do not add anything to it or take anything away from it.
Fall from Grace
There are serious consequences for putting yourself back under the Old Covenant Law system.
Galatians 5:4 CSB
You who are trying to be justified by the law are alienated from Christ; you have fallen from grace.