If it was revealed to Peter at that moment, then his reaction to Cornelius at Acts 10 would have been irrational.
It was stated by another poster that Peter came to understand the gospel through Paul in Acts 15,
but as we know he was already proclaiming that the gift of the Spirit is granted though faith in Christ in Acts 2:38.
The account in Acts 10 in which he perceived that it was for both Jew and Gentile, was also by divine revelation.
Then Peter opened
his mouth and said: “In truth I perceive that God shows no partiality. But in every nation whoever fears Him and works righteousness is accepted by Him. You know the word which
God sent to the children of Israel, preaching peace through Jesus Christ—He is Lord of all— Acts 10:34-36
He commanded us to preach to the people, and to testify that it is He who was ordained by God
to be Judge of the living and the dead.
To Him all the prophets witness that, through His name, whoever believes in Him will receive remission of sins.”
The Gift of the Holy Spirit was poured on the Gentiles
While Peter was still speaking these words, the Holy Spirit was poured on all those who heard the word. Acts 10:42-44
Again in Acts 11,
Peter Defends God’s Grace (NKJV)
If therefore God gave them the same gift as
He gave us when we believed on the Lord Jesus Christ, who was I that I could withstand God?”
When they heard these things they became silent; and they glorified God, saying, “Then God has also granted to the Gentiles repentance to life.” Acts 11:15-18