Who was following Paul and Barnabas around and troubling their new congregations?
The Judaizers were troubling the new congregations. As Paul and Barnabas labored from Antioch and moved into Asia Minor and Greece, these Judaizers constantly subjected Paul's converts to the demand that they keep the Law of Moses, practice circumcision, and so forth.
Les explains that the church in Antioch had become predominantly Gentile, and Paul and Barnabas labored there and also moved out from Antioch into the Gentile world of Asia Minor and Greece. Everywhere they went, their little congregations were constantly subjected to the Judaizers, who tried to bring them back under the Law. These Judaizers claimed that Paul's converts could not be saved unless they kept the Law of Moses, practiced circumcision, and so forth. Finally, after many years, the issue came to a head, and Paul and Barnabas, by the Lord's direction, were sent up to Jerusalem to confront Peter and the hierarchy there. Paul rehearses this in Galatians chapter 2, and Luke records the same meeting in Acts chapter 15.