Then you've established the covenant based upon human DNA. Which is contrary to
Mat 3:9 And think not to say within yourselves, We have Abraham to our father: for I say unto you, that God is able of these stones to raise up children unto Abraham.
I'm sure those stones would also possess the DNA of Abraham. After all, it is a covenant with him and HIS SEED and as per the covenant promises of God the stones would definitely have Hebrew DNA.
Rom 2:29 But he is a Jew, which is one inwardly; and circumcision is that of the heart, in the spirit, and not in the letter; whose praise is not of men, but of God.
It has nothing to do with the DNA of men.
When God made covenant with Abram the Hebrew and circumcision was performed, this covenant produced a non-Hebrew people we call Gentile. Before covenant there were no Gentiles.
Israel is the natural Olive tree and a Jew and when Jews began to be born again of the Spirit Israel became spiritual Israel. Saul is not teaching only Jewish Christians are Jew. He is making distinction between obedience and disobedience and the Jews were both. Here, Saul writes to Jewish Christians at Rome with proselytes, God-Fearers, and a few hard-core, uncircumcised, non-covenant, idol-worshiping Gentiles. But he's addressing Jewish Christians at Rome.
17 Behold, thou art called a Jew, and restest in the law, and makest thy boast of God,
18 And knowest his will, and kapprovest the things that are more excellent, being instructed out of the law;
19 And art confident that thou thyself art a guide of the blind, a light of them which are in darkness,
20 An instructor of the foolish, a teacher of babes, which hast the form of knowledge and of the truth in the law. 21 Thou therefore which teachest another, teachest thou not thyself? thou that preachest a man should not steal, dost thou steal?
22 Thou that sayest a man should not commit adultery, dost thou commit adultery? thou that abhorrest idols, dost thou commit sacrilege?
23 Thou that makest thy boast of the law, through breaking the law dishonourest thou God?
24 For the name of God is blasphemed among the Gentiles through you, as it is written.
25 For circumcision verily profiteth, if thou keep the law: but if thou be a breaker of the law, thy circumcision is made uncircumcision.
26 Therefore if the uncircumcision keep the righteousness of the law, shall not his uncircumcision be counted for circumcision?
27 And shall not uncircumcision which is by nature, if it fulfil the law, judge thee, who by the letter and circumcision dost transgress the law?
28 For he is not a Jew, which is one outwardly; neither is that circumcision, which is outward in the flesh:
29 But he is a Jew, which is one inwardly; and circumcision is that of the heart, in the spirit, and not in the letter; whose praise is not of men, but of God. Rom. 2:17–29.
Saul's letter to Jewish Christians at Rome as a rabbi writes and argues a point about obedience and disobedience. It's a Pharisaical form of debate. First a premise, then Scripture and commentary supporting or refuting what's being discussed, then a ruling is given. The Talmud is full of this form of debate, but Saul is not debating an issue with other rabbis, he's debating within himself.
1
What advantage then hath the Jew? or what profit is there of circumcision?
2
Much every way: chiefly, because that unto them were committed the oracles of God.
3
For what if some did not believe? shall their unbelief make the faith of God without effect?
4 God forbid! Rom. 3:1–4.
What Saul is doing is called "Halakah." Look it up. His Roman letter is full of this form of commentary. Their rabbinic Talmud is full of such discussions, especially the statement "God forbid."
Joh 1:11 He came unto his own, and his own received him not.
Joh 1:12 But as many as received him, to them gave he power to become the sons of God, even to them that believe on his name:
Joh 1:13 Which were born, not of blood, nor of the will of the flesh, nor of the will of man, but of God.
Christ is the fulfillment of all covenants and prophecies about Him. He didn't abolish the Law and He didn't change the Law, and the Law is still valid for the people of God. Even Saul obeyed the Law after meeting Yeshua Messiah. The elders of the Temple address Saul:
23 Do therefore this that we say to thee: We have four men which have a vow on them;
24
Them take, and purify thyself with them, and be at charges with them, that they may s
have their heads: and all may know that those things, whereof they were informed concerning thee, are nothing;
but that thou thyself also walkest orderly, and keepest the law. Acts 21:23–24.
Saul was and is and remained a rabbi and continued to obey the Law of Moses. True, Biblical Christianity is Completed Judaism.