What did the men from Judea teach the Gentiles in Acts 15:1?
They taught the Gentile believers that circumcision according to the manner of Moses was necessary for salvation, saying, “Unless you be circumcised after the manner of Moses, you cannot be saved.” This was the false teaching Paul and Barnabas had to refute.
Les explains that Acts 15:1 records certain men coming down from Judea to the Gentile brethren and teaching that unless they were circumcised after the manner of Moses, they could not be saved. He notes this was false teaching coming into their midst, which Paul had to constantly refute. It caused no small dissension and disputation, so Paul and Barnabas and certain others were determined to go up to Jerusalem to the apostles and elders about this question. At Jerusalem, certain of the sect of Pharisees rose up.
And certain men which came down from Judaea taught the brethren, and said, Except ye be circumcised after the manner of Moses, ye cannot be saved.