Only one who didn’t have complete faith in Christ’s sacrifice alone as sufficient atonement for his sins, would think an additional work is required to save him. The Galatians believed the Gentile converts had to be circumcised to become Christians. Paul rebukes them, because they’ve missed the whole point. The whole reason for preaching to the Gentiles was to show that those outside the Mosaic covenant would still be acceptable to God. To require a Gentile to kind of sneak his way into Judaism through circumcision is an attempt to downplay the wonderful grace of God. By saving Gentiles, God is saying that the law is not what saves people. It is faith in Christ’s sacrifice. Because the Jews had been disobedient to God, God opened the gates of Heaven to the Gentiles. To make Gentiles look like the Jews after their conversions is to distort the great picture of mercy and divine prerogative displayed by God in the New Testament.