What did the Judaizers try to convince Paul to require of Gentile believers?
The Judaizers sought to convince Paul that Gentile believers must submit to circumcision and observe the Mosaic Law. They pressed him to add legal requirements to the gospel of grace, but Paul adamantly refused, defending salvation by grace apart from Law and legalism.
Les explains that the Judaizers and Jewish leaders, including Peter and the eleven, were coming down hard on Paul for teaching his message of grace to Gentiles. They tried to convince him, as earlier in Galatians, that he had to practice circumcision and keep the Law for these Gentile believers. Paul adamantly refused. Later, Peter realizes God had used him to take the Word to the Gentile Cornelius, and he asks why test God by putting a yoke on the neck of the disciples. That word means the believers in Antioch who had become believers of Paul's Gospel, not under Law or legalism, which the Judaizers were trying to put there.