What did Peter witness at Cornelius' house about how God saves a Gentile?
At the house of Cornelius, Peter witnessed that God would save a Gentile without the Gentile ascribing to Judaism, without repentance, and without water baptism. The Gentiles were saved even before Peter could proceed that far. Peter later recalled this about fourteen years earlier while defending Paul in the Acts 15 controversy.
Les explains that Acts 15 records the controversy between Peter and the eleven in Jerusalem and Paul concerning Gentiles being saved apart from Judaism, without circumcision, and without being commanded to keep the Law. Pharisees demanded that Gentile believers be circumcised and keep the Law of Moses. Paul refused. Peter finally came to Paul's defense, remembering about fourteen years earlier at Cornelius' house. There he had witnessed that God would save a Gentile without ascribing to Judaism, without repentance and water baptism; they were saved even before Peter got that far.