Acts 18:1-4 NIV “After this, Paul left Athens and went to Corinth. There he met a Jew named Aquila, a native of Pontus, who had recently come from Italy with his wife Priscilla, because Claudius had ordered all Jews to leave Rome. Paul went to see them, and because he was a tentmaker as they were, he stayed and worked with them. Every Sabbath he reasoned in the synagogue, trying to persuade Jews and Greeks.”
We find a consistent pattern in Paul's journeys; wherever he goes, he finds the Jewish community. Wherever he goes, we find him at the synagogue “every Sabbath”; there is no record that Paul did anything “every Sunday”. Among the Jews at the synagogue, he also finds “Greeks”. The people who come to believe his message are largely drawn from this demographic group. This has implications for the character of the believing groups that he leaves behind— they are composed, largely, of Jews and Jewish-influenced people. Since we have no record of a break with Jewish customs and patterns of worship, we would expect that these assemblies (churches) would continue to meet much as they had done before. Perhaps the community splits in disagreement over Paul's teaching, but the nucleus drawn from the original community would have formed a synagogue of believers that was similar in many ways to the one from which they came.
Acts 18:5-8 NRSV “When Silas and Timothy arrived from Macedonia, Paul was occupied with proclaiming the word, testifying to the Jews that the Messiah was Jesus. When they opposed and reviled him, in protest he shook the dust from his clothes and said to them, “Your blood be on your own heads! I am innocent. From now on I will go to the Gentiles.” Then he left the synagogue and went to the house of a man named Titius Justus, a worshiper of God; his house was next door to the synagogue. Crispus, the official of the synagogue, became a believer in the Lord, together with all his household; and many of the Corinthians who heard Paul became believers and were baptized.”
It was not all the Jews in the Corinth synagogue who opposed Paul; in fact, the “ruler” of the synagogue was among those who believed. On leaving the synagogue, Paul did not go far. The impression isn't that Paul lead a break away from the Jewish community, but that the community divided. Paul’s protest about going to the Gentiles does not mean he changed his methods; he continues to meet in the synagogues. See Acts 18:19 and 19:8.
Acts 18:14-15 NRSV “Just as Paul was about to speak, Gallio said to the Jews, “If it were a matter of crime or serious villainy, I would be justified in accepting the complaint of you Jews; but since it is a matter of questions about words and names and your own law, see to it yourselves; I do not wish to be a judge of these matters.””
Gallio, the proconsul, saw the dispute between Paul and the unbelieving Jews as an internal Jewish dispute. Nether Paul or his opponents said anything to suggest that Paul was not Jewish.
Acts 18:18 ESV “… At Cenchreae he had cut his hair, for he was under a vow.”
See Numbers 6:1-21. The nature of Paul's vow is not entirely clear. It resembles the nazirite vow. Paul later continues the prescribed steps for this vow when he arrives in Jerusalem. In any case, Paul is following procedures outlined in the Torah— this is a very Jewish behavior.
Acts 18:19-21 NRSV “When they reached Ephesus, he left them there, but first he himself went into the synagogue and had a discussion with the Jews. When they asked him to stay longer, he declined; but on taking leave of them, he said, “I will return to you, if God wills.” Then he set sail from Ephesus.”
Paul continued his pattern of seeking out the synagogues in the cities he visits. There is no mention of opposition to Paul's teachings at the synagogue in Ephesus; in fact, they want to hear more.
Acts 18:22 NASB “When he had landed at Caesarea, he went up and greeted the church, and went down to Antioch.”
Acts 18:22 NRSV “When he had landed at Caesarea, he went up to Jerusalem and greeted the church, and then went down to Antioch.”
The NET Notes are helpful for making sense of this verse. “The words “at Jerusalem” are not in the Greek text, but are implied by the participle anabas. The expression “go up” refers almost exclusively to the direction of Jerusalem, while the corresponding “go down” refers to directions away from Jerusalem. Both expressions are based on a Hebrew idiom. Assuming Jerusalem is meant, this is another indication of keeping that key church informed.… Paul was trying to honor a vow, which also implies a visit to Jerusalem.”
This text is evidence that Paul respected the authority of the “zealous for the law” leadership in Jerusalem. Paul was not a loose-cannon; he is not working independently of the Jewish believers nor is he in opposition to them. Paul's hast in leaving Ephesus may have been related to his vow (18:18), in which case, his visit to Jerusalem is evidence that he was following the Torah prescribed steps for fulfilling a nazirite vow. In any case, Paul seems to hold Jerusalem as a place of special importance and honor. (See Acts 24:11-12)
Acts 18:24-26 NIV “Meanwhile a Jew named Apollos, a native of Alexandria, came to Ephesus. He was a learned man, with a thorough knowledge of the Scriptures. He had been instructed in the way of the Lord, and he spoke with great fervor and taught about Jesus accurately,… He began to speak boldly in the synagogue.”
A knowledge of Scriptures— meaning the Hebrew Scriptures, the Torah, Prophets and Writings of the Old Testament— were important to the apostles and early believers. They were not “New Testament Christians” who neglected or rejected the “Jewish Bible”. Paul is not the only believer with the custom of synagogue attendance.
Acts 18:28 NRSV “for he powerfully refuted the Jews in public, showing by the scriptures that the Messiah is Jesus.”
Apollos himself was Jewish as were Priscilla and Aquila. He entered into debate with fellow Jews who were not believers; however, many other Jews were believers. His debate was about the identity of the Messiah; it was not a debate against the Law or other Jewish customs.