Galatians 5:3

for I have five brothers—in order that he may warn them, so that they will not also come to this place of torment.’

Some men came down from Judea and began teaching the brothers, “Unless you are circumcised according to the custom of Moses, you cannot be saved.”

But some of the sect of the Pharisees who had believed stood up, saying, “It is necessary to circumcise them and to command them to keep the Law of Moses.”

Behold I, Paul, say to you that if you receive circumcision, Christ will be of no benefit to you.

For whoever keeps the whole law and yet stumbles in one point, he has become guilty of all.

The one who believes in the Son of God has this witness in himself. The one who does not believe God has made Him a liar, because he has not believed in the witness which God has borne witness about His Son.