The real circumcision is of the heart. That is what really counts, that is what will make it so you can live, as it says in Deut 30:6.

God will one day punish ALL those uncircumcised
in in heart.

“Behold, the days come, says Yahweh, that I will punish ALL those who are circumcised in their uncircumcision: 26 Egypt, and Judah, and Edom, and the children of Ammon, and Moab, and all that have the corners of their hair cut off, who dwell in the wilderness; for all the nations are uncircumcised, and all the house of Israel are uncircumcised in heart. ”
Jer 9:25 WEB emphasis added.

Jeremiah warned the people, and told them it was circumcision of the heart which counted.

“Circumcise yourselves to Yahweh, and take away the foreskins of your heart, you men of Judah and inhabitants of Jerusalem; lest my wrath go forth like fire, and burn so that none can quench it, because of the evil of your doings.”
Jer 4:4 WEB

These prophets speaking by the Holy Spirit of God should have been enough.

But some later wanted physical circumcision for all.

There was a big fight in the early church, as described in Acts 15, but physical circumcision was never required. The real circumcision was always of the heart.

So what is a real Jew, if not about physical circumcision?

“28 For he is not a Jew who is one outwardly, neither is that circumcision which is outward in the flesh; 29 but he is a Jew who is one inwardly, and circumcision is that of the heart, in the spirit not in the letter; whose praise is not from men, but from God.”
Rom 2:28-29 WEB

And how would this work out with the Gentiles?

Paul says they were,

“11 in whom you were also circumcised with a circumcision not made with hands, in the putting off of the body of the sins of the flesh, in the circumcision of Christ; 12 having been buried with him in baptism, in which you were also raised with him through faith in the working of God, who raised him from the dead. 13 You were dead through your trespasses and the uncircumcision of your flesh. He made you alive together with him, having forgiven us all our trespasses,”
Col 2:11-13 WEB

It is the inner man of the heart that counts.

That is true even of our initial test of faith, baptism.

“Peter said to them, “Repent, and be baptized, everyone of you, in the name of Jesus Christ for the forgiveness of sins, and you will receive the gift of the Holy Spirit.”
Acts 2:38 WEB

But it is not just about a bath. Peter compares it to the waters that floated Noah’s ark.

“This is a symbol of baptism, which now saves you – not the putting away of the filth of the flesh, but the answer of a good conscience toward God, through the resurrection of Jesus Christ,”
1Pe 3:20 WEB

WEB is the World English Bible, a copyright free revision
of the original ASV American Standard Version 1901