Why were the believers in Jerusalem still under the law after Pentecost?
The believers in Jerusalem remained under the law after Pentecost because God had not yet revealed the secret of grace going to the Gentiles. He was still dealing with the nation of Israel under the law. Their law-keeping mentality caused them to contend with Peter for eating with uncircumcised Gentiles.
Les teaches that the believers in Jerusalem were still under the law seven or eight years after Pentecost because God had not yet revealed the secret of grace going to the Gentiles. They were believing Jews of the circumcision who contended with Peter, arguing that he went into men uncircumcised and ate with them. Their mentality was still law: Gentiles were uncircumcised dogs, Gentile food was not kosher, and they could not visit with Gentiles. God was still dealing with the nation of Israel under the law. Les also points to Acts 22, where Paul describes Ananias as a devout man after the law, showing even he was a law-keeping Jew. Peter himself was not aware that God was going to the Gentiles.