They can do this because a person is not a true Jew if he is only a Jew in his physical body; true circumcision is not only on the outside of the body.
Give yourselves to the service of the Lord, and decide to obey him, people of Judah and people of Jerusalem. If you don’t, my anger will spread among you like a fire, and no one will be able to put it out, because of the evil you have done.
the people of Egypt, Judah, Edom, Ammon, Moab, and the desert people who cut their hair short. The men in all those countries are not circumcised. And the whole family of Israel does not give itself to serving me.”
You were not born Jewish. You are the people the Jews call “uncircumcised.” Those who call you “uncircumcised” call themselves “circumcised.” (Their circumcision is only something they themselves do on their bodies.)
And that water is like baptism that now saves you—not the washing of dirt from the body, but the promise made to God from a good conscience. And this is because Jesus Christ was raised from the dead.
I know your troubles and that you are poor, but really you are rich! I know the bad things some people say about you. They say they are Jews, but they are not true Jews. They are a synagogue that belongs to Satan.