They were not Jewish according to the Bible if they were Christian.
Three thousand Jews were born again as recorded in Acts by Luke and they were ALL Jewish Christian or Christ-followers. Jesus Christ was Promised to the Hebrew people in order to save the Hebrew people, hence His Name "Jesus" for He shall save His people from their sin (Matt. 1:21.) Jesus didn't die to atone for non-Hebrew Gentiles. He came to atone for the sins of the children of Israel and only they are recipients of eternal life.
The animal sacrifice under the Law was to atone for the sins of the children of Israel as commanded by the Law and this was done yearly until God would send forth His Son under the Law made of a woman to redeem those under the Law and this identifies the children of Israel.
The high priest never left Israel and go to the Gentile people that surround them and offer sacrifices for them or pray for them. The high priest was commanded by God in the Law to offer animal sacrifices to atone for the sins of the children of Israel. And since Scripture cannot be broken and Jesus came to fulfill the Law, then this fulfilling included to die as substitute in place of the animal so that by His very own blood would be shed for the sins of the children of Israel and only them as they were the people under the Law and God's chosen people ABOVE all the people in the earth. Jesus fulfilled the Law and died for the sins of the children of Israel in same fashion as the animals were sacrificed for the sins of the children of Israel except His sacrifice was once and for all the children of Israel as saith the Law.
4 But when the fulness of the time was come, God sent forth his Son, made of a woman,
made under the law,
5
To redeem them that were under the law, that we might receive the adoption of sons. Gal. 4:4–5.
And those that were under the Law were the children of Abraham.
In your mind they may be Jewish. But not in the language of the Bible. They may have been Jews before they got born again or they may have been Gentiles.
Again, Jesus died for the sins of the children of Israel as saith the Law. If you want to believe in lies that state Jesus died for the whole world then you teach universalism which isn't true. For if Jesus died for the whole world, then why aren't the whole world saved? Was there something wrong with His sacrifice?
Once saved God refers to them as Christians. Not Jews. Not Gentiles. And not Jewish Christians.
Those that awaited Messiah were Christian. Moses was Christian. David was Christian. Every Hebrew who awaited the coming of their Messiah and Deliverer were Christian but that's the Greek name. The Hebrew name is Messias. And the children of Israel all awaited His coming and thus were Christ/Messiah followers.
And the spirit was not poured out in the upper room since 3 thousand men could not fit in the sleeping area for men. They were in the Temple.
Can't you read?
5 And there were dwelling at Jerusalem Jews, devout men,
out of every nation under heaven.
6 Now when
this was noised abroad,
the multitude came together, and were confounded, because that every man heard them speak in his own language.
7 And they were all amazed and marvelled, saying one to another, Behold, are not all these which speak Galilaeans?
8 And how hear we every man in our own tongue, wherein we were born?
9 Parthians, and Medes, and Elamites, and the dwellers in Mesopotamia, and in Judaea, and Cappadocia, in Pontus, and Asia,
10 Phrygia, and Pamphylia, in Egypt, and in the parts of Libya about Cyrene, and strangers of Rome, Jews and proselytes,
11 Cretes and Arabians, we do hear them speak in our tongues the wonderful works of God.
12 And they were all amazed, and were in doubt, saying one to another, What meaneth this?
13 Others mocking said, These men are full of new wine.
Acts 2:5–13.
Matching the languages that were represented that morning shows us from where these Jews living in Gentile lands came from.
And these same Jews that were born again - three thousand - went back to their homes in Gentile lands taking with them an outline of Peter's sermon, their experiences with the Holy Spirit of Promise:
....and ye shall receive the
gift of the Holy Ghost.
39
For the promise is unto you, [Jews] and to your children, and to all [Jews] that are afar off, even as many as the Lord our God shall call. Acts 2:38–39.
The Holy Spirit was NEVER Promised to Gentiles. Scripture cannot be broken. Thus, the Holy Spirit of Promise PROMISED to the children of Israel in many places in Scripture - especially Jeremiah 31:31-34, was a Promise made to God's covenant people - NOT to Gentiles. So, if Scripture cannot be broken, then the only people who were marked to receive the Holy Spirit would be those to whom He was Promised that that identifies the children of Israel - Jews.
But if you want to violate Scripture, if you want to break Scripture, then continue to believe in something not true and that thing that is not true is the teaching that non-Hebrew Gentiles were promised the Holy Spirit of Promise. Go ahead and post your evidence, post your Scripture that says the Holy Spirit was promised to Gentiles.
Psst...there are no such Scripture. So, where does that teaching come from if it cannot be found in Scripture?
Hmmm?