What did Peter tell Cornelius about a Jew keeping company with a Gentile?

Les explains that Peter's words at Cornelius's threshold reveal that the Jerusalem believers were still basically law keepers and had not comprehended Paul's gospel of grace. Earlier, at the vision of the sheets, Peter said, "Not so, Lord," because he had never gone contrary to the law and ate kosher. At Cornelius's door, Peter said Cornelius knew it was an unlawful thing for him, a Jew, to keep company with a man of another nation. If Peter had understood grace, that thought would not have crossed his mind; he should have been thrilled to enter the military officer's house. But it was bugging him, for as a good Jew, according to the law, he could not go in. God, however, had made plain that this was what He wanted. This was part of the controversy, as Jewish emissaries from Jerusalem undermined Paul's congregations.