How did the Jews with Peter react when they saw Gentiles being saved?
The Jews who accompanied Peter to the house of Cornelius were astonished when they saw the evidence that Gentiles were being saved. Acts 10:45 says those of the circumcision who believed, who came with Peter, were astonished because the gift of the Holy Ghost was poured out on the Gentiles.
Les explains that Peter took six Jews with him to the house of Cornelius, making seven including Peter, and notes that seven is God's perfect number. When those seven Jews reached Cornelius's house and saw the evidence of Gentiles being saved, they were astonished. Les emphasizes this had never happened before, and that Gentiles were not saved earlier at John the Baptist or Pentecost; it was all Jewish. For a Gentile to be saved was an astonishment. Acts 10:45 confirms that those of the circumcision who believed, who came with Peter, were astonished because the gift of the Holy Ghost was poured out on the Gentiles.