I chuckle at this one. Here, Jesus clearly told the disciples to take this good news to the "nations" (same word for "gentiles), God lovingly gave them both power and the ability to communicate in all sorts of languages, and yet the disciples were clearly amazed when Cornelius shows up. Thankfully they took the good news to the rest of the world once persecution arose in Jerusalem. If not, I likely would never had heard, being gentile.
Additional context:
Jews (to include the Lord himself Matt 15:26) often referred to Gentiles as unclean "dogs". (See Matt 7:6; Lk 16:21)
Gentiles were considered bastard's outside of covenant seals, so ungodly, simply being in their presence could make a Jew ceremonially unclean. (See Jn 11:28 below)
Eph 2:
11 Wherefore remember, that ye being in time past Gentiles in the flesh, who are called Uncircumcision by that which is called the Circumcision in the flesh made by hands;
12 That at that time ye were without Christ, being aliens from the commonwealth of Israel, and strangers from the covenants of promise, having no hope, and without God in the world:
(NOTE: Gentiles were what? """Strangers from the covenants of promise""" """having no hope""" """without God in the world"""
John 18:28 Then led they Jesus from Caiaphas unto the hall of judgment: and it was early; and they themselves went not into the judgment hall, lest they should be defiled; but that they might eat the passover.
(NOTE: The Jews wouldn't even walk into the Roman/gentile judgment hall, lest they should be defiled/become unclean. They wouldn't enter because they wanted to eat the Passover meal on the next day. There was a 7 day ritual cleansing period that had to be honored once deemed unclean. Contact with a dead person or animal, a woman during her menstrual cycle etc.
Acts 10:28 happens many years after Acts 2 Pentecost. Peter has a vision & argues, 3 TIMES, with the Lord about things clean & unclean. The Lord tells Peter, if I say it's clean, IT'S CLEAN, now go!
Acts 10:28 Peter said unto them, Ye know how that it is an ""unlawful"" thing for a man that is a Jew to keep company, or come unto one of another nation; but God hath shewed me that I should not call any man common or unclean
(NOTE: Peter tells Cornelius a gentile. IT'S UNLAWFUL for a Jew to keep company with a gentile)
Acts 10:45 And """they of the circumcision which believed were astonished""", as many as came with Peter, because that on the Gentiles also was poured out the gift of the Holy Ghost.
(NOTE: This is aprox 7 yrs after the Temple Mt Pentecost where JEWS only had received the gift of the indwelling H/S. The Jews here (Peter included) that witnessed the gentiles receiving the gift of the indwelling Holy Spirit were ASTONISHED. If gentiles had received the Holy Spirit at Pentecost, WHY, were these Jews (to included Peter) ASTONISHED here?)
Finally:
Paul is at Stephen's stoning (4 yrs after Pentecost) cheering the crowd on. Next, Paul is on the road to Damascus, meets the Lord & is soon converted. Next, Paul travels to Arabia (Gal 1:7) Paul returns 3 years later (Gal 1:18). Its now at least 7 years after Pentecost.
It gets really ugly for Paul here. We are way beyond Acts 2 Pentecost here:
Acts 21:28-36 Jews that were aware of Paul's dealings with gentiles, throw Paul out of the Temple, begin to beat him to death. Roman soldiers show up & pull Paul from the mob.
Acts 21:37- Acts 22:20: Paul reasons with the Roman in charge & is allowed to address the crowd. They listen to Paul's conversion testimony until verse 21
Acts 22:21 Paul say's he was sent to proclaim God to the gentiles & the Jewish crowd hears the word GENTILE and once again go ballistic & try to KILL Paul.
I adamantly reject the notion at the Acts 2 Pentecost. A Temple Mt full of devote law keeping Jews. Stood & remained peaceful while a bunch of UNCLEAN gentiles are running around speaking in tongues?