What was the mentality of the Jerusalem believers after Pentecost?

The Jerusalem believers still had a law mentality. They contended with Peter for entering among uncircumcised men and eating with them, insisting Gentiles were uncircumcised and that kosher separation must be maintained. Even seven or eight years after Pentecost, they had not yet understood God's grace extending to Gentiles.

Les explains that the believing Jews in Jerusalem were still under the law. When Peter returned to Jerusalem, those of the circumcision contended with him, arguing that he went to uncircumcised men and ate with them. Their mentality was that you cannot eat Gentile food because it is not kosher, and you cannot visit Gentiles, whom they considered 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 Israel under the law. Les also points to Ananias in Acts 22 as a devout man after the law, illustrating that even early Jewish believers remained law-keeping.

What was the mentality of the believing Jews in Jerusalem seven or eight years after Pentecost?

Seven or eight years after Pentecost, their mentality remained strictly law-based. They contended with Peter for entering uncircumcised men's company and eating with them, insisting Gentile food was not kosher and Gentiles were uncircumcised dogs. God had not yet revealed the secret of grace going to the Gentiles, so He was still dealing with Israel under the law.