Thank you for your post and for your points.
The New Covenant does not invalidate the Word of God. It re-affirms it (see Jeremiah 31:31-33). That's why Paul said,
Gal 3:19, 21-24 "Why then the Law? It was added because of transgressions, until the Seed should come to those to whom it had been promised, being ordained through angels in the Mediator's hand.
Is the Law then against the promises of God? Let it not be said! For if a law had been given which could have given life, indeed righteousness would have been out of Law. But the Scripture shut up all under sin, so that the promise by faith of Jesus Christ might be given to those who believe.
But before faith came, we were kept under Law, having been shut up to the faith about to be revealed. So that the Law has become a trainer of us until Christ, that we might be justified by faith."
The New Covenant does, indeed,
re-affirm God's Word, and does not change or invalidate it. It does not take a body of instruction about which it is said, "The sum of your word is truth, and every one of your righteous rules endures forever." (Psalm 119:160 ESV) and cause it to no longer serve for the instruction of those who believe, or no longer comprise the truth, or no longer endure. In the very passage you just quoted (Gal 3) Paul is clear to affirm: "the law, which came 430 years afterward, does not annul a covenant previously ratified by God, so as to make the promise void" (3:17). By "promise" Paul refers to the Abrahamic covenant, and by Law he refers to the Mosaic law,
which his opponents at the time believed justified and included one in the promises of salvation. This is what Paul is arguing:
the law cannot/does not/is not intended to justify. I am confident that we are in agreement on that point, at least.
But the New Covenant also does not change the contents of the covenant. The radical change, the manner in which the New Covenant was unlike the Old Covenant, is that it was now God who was/is responsible to write His law (the same law, not a different or truncated one) on the hearts of His people. While previously the people were responsible to keep their promise, "All that the LORD has spoken we will do, and we will be obedient" (Ex 24:7), and to "Circumcise therefore the foreskin of your (plural) heart, and be no longer stubborn" (Deu 10:16), now God is responsible, for he promises, "But this is the covenant that
I will make with the house of Israel after those days, declares the LORD:
I will put my law within them, and
I will write it on their hearts. And
I will be their God, and they shall be my people" (Jer 31:33). You may note that it is the same promise God has been making all along, since Gen 17:7, Ex 6:7, Lev 26:12, etc: "And I will walk among you and will be your God, and you shall be my people." It may also be helpful to notice that everything God says and does is to restore the state of Eden: "I will walk among you." Everything new is old again, to turn a common phrase on its head.
This promise never varies, it is in fact, the meta-goal of God's redemptive acts in history. "And I heard a loud voice from the throne saying, "Behold, the dwelling place of God is with man. He will dwell with them, and they will be his people, and God himself will be with them as their God." (Revelation 21:3 ESV)
Likewise, God's character never changes, and similarly our perpetual command never changes: "Be imitators of God, therefore, as dearly loved children." (Ephesians 5:1 NIV) How shall we know what God's character is? The Law, the Gospels, and the Spirit: a description, an example, and the "finger of God," which is writing His laws on our heart, rather than on stone tablets. When a body of instruction moves from stone tablets (description) to living tablets (our hearts) it does not go away and is not replaced, but is now quickened, or enlivened.
Nothing you say or which you quote changes the fact that Jesus and Paul made a summation of all the law, making it abundantly clear what laws they regarded as moral and eternally applicable, and how those laws were fulfilled only by Christ, and how they can be produced as CHRIST'S fruit only in those who abide in Christ and live by faith in Him and in His righteousness.
It should be patently obvious that a summation does not replace or alter: it summarizes. Just as the 10 Words summarize the "613" commandments of the Mosaic Law, and just as Micah summarizes the entire law with "He has told you, O man, what is good; and what does the LORD require of you but to do justice, and to love kindness, and to walk humbly with your God?", so does Jesus summarize all God's law with the "2 Great Commandments" and Paul summarizes them with, "For the commandments, "You shall not commit adultery, You shall not murder, You shall not steal, You shall not covet," and
any other commandment, are summed up in this word: "You shall love your neighbor as yourself." Love does no wrong to a neighbor; therefore love is the fulfilling of the law." (Romans 13:9-10 ESV)
You will notice, I hope, that the "fulfilling" does not replace or change the commandments, but keeps them. To summarize makes something easier to understand, to evaluate, to comprehend, to live in accord with. It never replaces or changes something.
So when we read in Deuteronomy: "When you build a new house, you shall make a parapet for your roof, that you may not bring the guilt of blood upon your house, if anyone should fall from it." (22:8), we are to consider ourselves instructed by that. Not threatened by losing our salvation if we do not do so, but taught what God would do in the scenario that people use their roofs in the same manner as we use our porch, deck, or balcony.
Furthermore, we are instructed on good government: there is no penalty for not building a parapet around your roof, unless someone falls from it, and then one is held guilty for failing to have properly (as God would have) loved their neighbor.
But in saying that only Christ can
perfectly fulfill God's law, we would agree, but it is also helpful to note that God's expectation is that the "righteous requirements" of His law will be walked out or fulfilled "
in us, who walk not according to the flesh but according to the Spirit." (Rom 8:4)
And, because it is biblical, I would also agree that the fruit of God's Spirit, which is present only in those who abide in Christ, is what produces the "good deeds" which we were created and subsequently saved in order to walk in. (Eph 2:10)
So where do we disagree? You have been presenting a case for a complicated reading of Scripture which attempts to describe how one can read the Bible so as to believe that certain of God's laws have been done away with, and we are only now instructed (essentially) by that which is repeated in the New Testament. I am hoping you will come to see that one doesn't have to work so hard to understand the Bible. The Scriptures are clear: be imitators of God, just like beloved children yearn to imitate their fathers.
Everything in Scripture, from Genesis to Revelation, tells us something about God's character, and we--not for our salvation, but in gratitude for it, and by virtue of its enabling--now seek to do what Jesus would do in any given situation, and every situation in Scripture is pertinent to our attempt to imitate Him.
The question of
how does x or y apply in my time and place is admittedly complex, but that is what we have an entire Body for, and that is why we have a Head and His Spirit within us.
So my advice to you would be (if you will forgive the presumption): IF you see anyone attempting to
earn their salvation by doing right, share with them the good news that salvation is by grace through faith in accepting the perfect life of Christ applied to their benefit. BUT, if you see anyone attempting to more perfectly imitate their Savior by living as He did (observing the calendar He observed, eating only those foods He ate, etc.)
out of their love for Him, bless them in their journey, and look to collaborate with them, as there are most certainly areas where you are more perfectly walking in the Spirit and areas where they are more perfectly walking in the Spirit, and we are both called to "exhort one another daily, and all the more as we see the Day approaching."