Hi d, Sorry, this is a little long- but it is what it is..... my answer

Rom 2:28-29 For he is not a Jew who is so outwardly, neither is circumcision that which is outward in flesh; but a Jew is he who is so inwardly, and circumcision is of the heart, in spirit, not in letter, of which the praise is not of men, but of God.
In romans chapters 1 & 2 Paul teaches us that those who keep the law written in their hearts are jews even if they don't know it. He also teaches that Jews who stand on the law but do not know the heart of the lawgiver are not Jews, though they have Jewish parents and knowledge of the law and the prophets, as our Lord also taught( I can from these stones raise up children to Abraham.....Think not you have Abraham as your father.....You are like Cain....The devil is your father)
Rom 7:4-6 Therefore, my brethren, you also were made to die to the Law through the body of Christ, so that you might be joined to another, to Him who was raised from the dead, in order that we might bear fruit for God. For while we were in the flesh, the sinful passions, which were aroused by the Law, were at work in the members of our body to bear fruit for death. But now we have been released from the Law, having died to that by which we were bound, so that we serve in newness of the Spirit and not in oldness of the letter.
Only a revelation of Jesus Christ suffices for righteousness, but that revelation is a manifestation of love and known only by God who sees (heb 4:12) the secrets of the heart, "Many will say unto Me on that day 'Lord, Lord'....I will tell them depart from me you lawless ones I never knew you." "Knowing" Jesus- a union of love in a broken and a contrite heart- is the new law that fulfills the old law. The old husband of the righteous is dead, the new husband is "the law of the Spirit of Life in Christ Jesus." Such as are in Him through this new love covenant do not serve sin, because they are in the new nature- tho they still wrestle with the world, the flesh and the devil. The mark of the prize of their "upward call" is to overcome.
2Co 3:1-18 You are our letter, written in our hearts, known and read by all men; being manifested that you are a letter of Christ, cared for by us,
written not with ink but with the Spirit of the living God, not on tablets of stone but on tablets of human hearts. Such confidence we have through Christ toward God.
Not that we are adequate in ourselves to consider anything as coming from ourselves, but our adequacy is from God, who also made us adequate as servants of a new covenant, not of the letter but of the Spirit; for
the letter kills, but the Spirit gives life. But if the ministry of death, in letters engraved on stones, came with glory, so that the sons of Israel could not look intently at the face of Moses because of the glory of his face, fading as it was, how will the ministry of the Spirit fail to be even more with glory? For if the ministry of condemnation( OT law) has glory, much more does the ministry of righteousness(Christ in you) abound in glory. For indeed what had glory, in this case has no glory because of the glory that surpasses it. For if that which fades away was with glory, much more that which remains is in glory. Therefore having such a hope, we use great boldness in our speech, and are not like Moses, who used to put a veil over his face so that the sons of Israel would not look intently at the end of what was fading away.
But their minds were hardened; for until this very day at the reading of the old covenant the same veil remains unlifted, because it is removed in Christ. But
to this day whenever Moses is read, a veil lies over their heart;but whenever a person turns to the Lord, the veil is taken away.
Now the Lord is the Spirit, and
where the Spirit of the Lord is, there is liberty. But we all, with unveiled face, beholding as in a mirror the glory of the Lord, are being transformed into the same image from glory to glory, just as from the Lord, the Spirit(by the Spirit of the Lord).
Those who are still in the letter have a veil over their faces. When they read the word they only see the letter. They cannot receive the spirit of wisdom and revelation in the knowledge of God, so they do not know the hope of their calling, the riches of His inheritance in the saints and the surpassing greatness of His power towards us who believe(Ephesians 1:12). They are falling in the wilderness. They cannot enter the promised land. They are walking in circles under the discipline of God, yet with his grace- but outside His rest.
Rom 10:1-4 Brethren, my heart's desire and my prayer to God for them is for their salvation. For I testify about them that they have a zeal for God, but not in accordance with knowledge. For not knowing about God's righteousness and seeking to establish their own, they did not subject themselves to the righteousness of God. For Christ is the end of the law for righteousness to everyone who believes.
Misplaced zeal is often at the heart of "legalism" which is approaching the new covenant from the letter, from the commandments, from the mind-first soul. It is those who are led by the Spirit who are the sons of God, they are being transformed by the renewing of their minds, serving in the newness of the Spirit, not in the fading oldness of the letter. When you have "Christ in you the hope of glory" you do not need the law, you have the divine nature, the mind of Christ, the incorruptible seed of the living word and the Holy Spirit who leads us into all truth.
Gal 4:1-5 Now I say, as long as the heir is a child, he does not differ at all from a slave although he is owner of everything, but he is under guardians and managers until the date set by the father. So also we, while we were children, were held in bondage under the elemental things of the world. But when the fullness of the time came, God sent forth His Son, born of a woman, born under the Law, so that He might redeem those who were under the Law, that we might receive the adoption as sons.
Gal 4:22-26 For it is written that Abraham had two sons, one by the bondwoman and one by the free woman. But the son by the bondwoman was born according to the flesh, and the son by the free woman through the promise. This is allegorically speaking, for these women are two covenants: one proceeding from Mount Sinai bearing children who are to be slaves; she is Hagar. Now this Hagar is Mount Sinai(Heb 12:18-21) in Arabia and corresponds to the present Jerusalem, for she is in slavery with her children. But the Jerusalem above(Heb12:22-25) is free; she is our mother.
Their are many Christians who are like Ismael, fathered by the spirit (Abraham) but mothered by the law (Hagar) and acting like Ishmael- they have a blessing and are a great nation but "their hands is against every man"(divisive, not united, no peace). Their are also Christians who are fathered by the spirit (Abraham) and mothered by Sarah ( our mother- the new Jerusalem from above who is free) but they are babes, so they are no different than slaves, they are "kept under tutors" until they grow in grace and begin to see the glorious freedom of the sons of God. We seek to bring people into a love relationship with Jesus that produces life. "Legalism" keeps the redeemed in slavery to man-made traditions based in wrong interpretations of the law of God and the unrighteous stewardships of men rather than the freedom that is ours in Christ.