Did Peter know Paul's gospel when he preached to Cornelius?
No, Peter did not yet know the gospel later revealed to Paul. At Cornelius’s house, Peter preached Jesus of Nazareth as crucified and raised, and that salvation was through His Name, not through the work of the cross as Paul would later proclaim.
Les explains that while Peter was preaching in Cornelius’s home, he had not said a word about the work of the cross for salvation by Jesus’ shed blood, as Paul would have done. Peter could only rehearse that Jesus of Nazareth, who had appeared to Israel, had been crucified, killed, raised from the dead, and was alive. In Acts 10:43 Peter said all the prophets witness that through His Name—not through His work of the cross—is salvation. So Peter as yet did not know Paul’s Gospel, but he did know that the Name of Jesus of Nazareth, the Messiah, the Son of God, was the vehicle for salvation. The Holy Spirit fell on the Gentiles while Peter was yet preaching, evidenced by tongues, and Peter was flabbergasted because the expected order of repentance, baptism, then Spirit did not happen.
To him give all the prophets witness, that through his name whosoever believeth in him shall receive remission of sins.
More Questions
What did Peter know about salvation before he knew Paul's gospel?
Peter as yet did not know Paul's gospel, but he did know that the Name of Jesus of Nazareth, the Messiah, the Son of God, was the vehicle for salvation.
What did Peter preach to the Gentiles about how sins are forgiven?
Peter preached that through His Name whoever believes in Him receives remission of sins — he said nothing about repenting and nothing about baptizing.