How long after Pentecost did the believers in Jerusalem still hold a law-keeping mentality?
The believers in Jerusalem still held a law-keeping mentality seven to eight years after Pentecost. They contended with Peter for entering uncircumcised men and eating with them, insisting Gentile food was not kosher and Gentiles were uncircumcised dogs, because God had not yet revealed the secret of grace going to the Gentiles.
Les explains that these were believing Jews of the circumcision who argued with Peter after he went up to Jerusalem. Their mentality was still law: they said he went into men uncircumcised and ate with them. They thought you cannot sit down and eat Gentile food because it is not kosher, and you cannot visit Gentiles, calling them uncircumcised dogs. This was still their mindset seven or eight years 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. Les also points to Ananias in Acts 22 as a devout man after the law, showing even he was a law-keeping Jew.