Acts 15:1

15:1 The reports of Paul’s and Barnabas’s direct contact with the Gentiles on the first missionary journey may have reached Judea and Jerusalem through John Mark after he returned home (13:13). Also, others from Antioch may have brought the news during Paul’s and Barnabas’s extended stay there. This caused the Jewish Christians to fear that their Jewish heritage was threatened; they thought that the converted Gentiles must be brought into Judaism through circumcision. Paul recognized that forcing Gentiles to be circumcised might make them think that salvation must be earned (cf. Gal. 2:15, 16). He knew that the Judaizers had to be opposed lest they hinder the extension of the gospel to the Gentiles (1 Thess. 2:14–16).