The original 12 apostles/disciples of Jesus were all Jewish. By Jewish I understand you to mean "of the twelve tribes of Israel"/ Israelites. Since one can interpret Jewish to be the religion, and there are Gentiles who adopt Judaism and are sometimes considered Jewish from a religious perspective, one needs to be careful with the term. But from a Hebrew/Israelite/race perspective, even the two understood replacements for Judas Iscariot (Matthias replaced by a process of the other 11, and/or Paul as a replacement directly by Jesus) were Jewish. It isn't until very late into some of Paul's letters that there is any mention of apostles who are not Jewish (mentioned with the title/description of apostle), such as Apollos.
If you go to the Wikipedia entry for the Apostles of Jesus, there is a list of the twelve with a link to a biography of each, but I had trouble finding reference to their Jewish heritage. It's like all articles on this subject that I found just assumed it was true without showing any evidence. I do know some of these Scripture declares it directly, but not for all.
I know inherently that this is true - all the 12 disciples were Jewish, but I'm having a hard time finding references to prove it.
Thanks to a comment from Mr. Bultitude, which speaks to the Jewishness of the names of the apostles, assuming that Thaddeus is actually Jude as most scholars believe:
- Each of their names has a Hebrew origin, with the exceptions of Andrew (Greek name, but Peter's brother) and Philip (Greek name, but from the same city as Peter and Andrew) and the possible exception of Thaddeus (probably Aramaic name, so still evidence that he's Jewish, and he's also identified with an apostle known as Jude, which is absolutely a Jewish/Hebrew name)
I saw a quote that Judas Iscariot was the only Judean, and the rest were Galilean. This may be confirmed at Pentecost in Acts 2:
1 Now when the day of Pentecost had come, they were all together in one place. 2 Suddenly a sound like a violent wind blowing came from heaven and filled the entire house where they were sitting. 3 And tongues spreading out like a fire appeared to them and came to rest on each one of them. 4 All of them were filled with the Holy Spirit, and they began to speak in other languages as the Spirit enabled them.
5 Now there were devout Jews from every nation under heaven residing in Jerusalem. 6 When this sound occurred, a crowd gathered and was in confusion, because each one heard them speaking in his own language. 7 Completely baffled, they said, “Aren’t all these who are speaking Galileans? 8 And how is it that each one of us hears them in our own native language? [ Acts 2:5-8 (NET) ]
If there is some way to show that all 12 (or 11 + Matthias) of the apostles were present at Pentacost (this follows from the narrative...), this may be a proof, though it feels somewhat weak. The issue is that Galilean may or may not necessarily imply Israelite/Hebrew/Jew.
A completely different way to tackle this may be to look at how the apostles behaved toward the question of spreading the gospel to non-Jews at the start.
While Jesus did bring the gospel to the Samaritan's directly (See the story of Jesus and the Samaritan women in John 4 - which completely surprised the disciples that he even spoke with them) it's not until well after the start of the church in Jerusalem that they even officially consider the possibility of extending the church to the gentiles. Even though Philip pretty quickly spread the gospel to the Ethiopian Eunuch (Acts 8:27-40), and others, apparently not the apostles, spread the word to gentiles (Acts 8:19-22):
19 Now those who had been scattered because of the persecution that took place over Stephen went as far as Phoenicia, Cyprus, and Antioch, speaking the message to no one but Jews. 20 But there were some men from Cyprus and Cyrene among them who came to Antioch and began to speak to the Greeks too, proclaiming the good news of the Lord Jesus. 21 The hand of the Lord was with them, and a great number who believed turned to the Lord. 22 A report about them came to the attention of the church in Jerusalem, and they sent Barnabas to Antioch. [ Acts 8:19-22 (NET) ]
In fact, it was so bad that God had to send Peter a vision and directly send him to Cornelius, a Gentle, and poured out his Spirit on them in order to finally get the point across to the church that the good news was for everyone, even though he told them that directly in the Great Commission. In fact, this was so against their teaching, that Peter had to go back and defend/explain his actions of even entering into a Gentile house, which was against the purification laws of the Jews:
1 Now the apostles and the brothers who were throughout Judea heard that the Gentiles too had accepted the word of God. 2 So when Peter went up to Jerusalem, the circumcised believers took issue with him, 3 saying, “You went to uncircumcised men and shared a meal with them.” 4 But Peter began and explained it to them point by point, saying, ... [ Acts 11:1-4 (NET) ]
Even after this the Gentiles were accepted, but then many started saying that the Gentiles had to essentially convert to Judiasm and obey all the Mosaic laws - which leads to "the Jerusalem Council" in Acts 15, where it was decided this line of reasoning was incorrect. Paul would end up fighting against that position for the rest of his career, with evidence found liberally throughout his letters.
So, what is the point of all this? If any of the original apostles were not Israelites, how could the infant church adopt a position that excluded Gentiles at the start?