What does Acts 17:1 mean?
In Philippi, apparently there were too few Jews for a synagogue, so Paul and Silas met God-fearing Gentile women by the river outside of town (Acts 16:13). In Thessalonica, they can return to their normal mode of operation: showing the Jews and the Gentiles who worship the Jewish God how Jesus of Nazareth fulfills the Old Testament prophecies of the Messiah. As in Pisidian Antioch, Paul explains how the Messiah had to die and rise again (Acts 13:26–41). And, as in Pisidian Antioch, some believe while the remaining run them out of town (Acts 13:48–51; 17:4–7).Synagogues developed after the destruction of the temple by Babylon (2 Chronicles 36:18–19). They provided a way for the Jews to learn what the Mosaic law expected of them without having to go to the temple or find a Levite. As the Jews spread across the Roman Empire, Gentiles joined in synagogue worship, realizing the Jews had knowledge of the true God. In Paul's time, the synagogue leaders regularly invited traveling Jews to speak to give a fresh perspective on the Scriptures. In Thessalonica, they invite Paul for three Sabbaths (Acts 17:2).
Paul's companions are Silas and Timothy; the third-person point of view indicates they left Luke in Philippi. Silas had come to Syrian Antioch with Paul and Barnabas after the council in Jerusalem and joined Paul's mission to plant churches after Paul and Barnabas fell out (Acts 15). Timothy, a young half-Jewish man, lived in Lystra. When Paul met him, he felt Timothy had the potential to be a good church leader and brought him along (Acts 16:1–3).
Amphipolis is 29 miles southwest of Philippi; Apollonia is another 24 miles southwest. Thessalonica is 30 miles west of Apollonia. Thessalonica is the largest city and capital of Macedonia. It is a "free city" of the Roman Empire; unlike in the Roman outpost of Philippi, it is legal to teach a non-state affirmed god (Acts 16:21). Paul's enemies don't charge them with promoting a foreign god but with teaching that Jesus is king in opposition to Caesar (Acts 17:7), much like the Sanhedrin did to Jesus (John 19:12).