Now when they had passed through Amphipolis and Apollonia, they came to Thessalonica, where was a synagogue of the Jews: Passed through Amphipolis - This city was the metropolis of the first division of Macedonia, as made by Paulus Aemilius: see the note on Acts 16:10. It was builded by Cimon, the Athenian general, who sent 10,000 Athenians thither as a colony. It stood in an island in the river Strymon, and had its name of Amphipolis because included between the two grand branches of that river where they empty themselves into the sea, the river being on both sides of the city.
Apollonia - This was another city of Macedonia, between Amphipolis and Thessalonica. It does not appear that St. Paul stopped at any of these cities: and they are only mentioned by the historian as places through which the apostles passed on their way to Thessalonica. It is very likely that in these cities there were no Jews; and that might have been the reason why the apostles did not preach the Gospel there, for we find them almost constantly beginning with the Jews; and the Hellenist Jews, living among the Gentiles, became the medium through which the Gospel of Christ was conveyed to the heathen world.
Thessalonica - This was a celebrated city of Macedonia, situated on what was called the Thermaic Gulf. According to Stephanus Byzantinus, it was embellished and enlarged by Philip, king of Macedon, who called it Thessalonica, the victory of Thessalia, on account of the victory he obtained there over the Thessalians; but, prior to this, it was called Thermae. But Strabo, Tzetzes, and Zonaras, say that it was called Thessalonica, from Thessalonica, wife of Cassander, and daughter of Philip. It is now in possession of the Turks, and is called Salonichi, which is a mere corruption of the original name.
A synagogue of the Jews - Ἡ συναγωγη, The synagogue; for the article here must be considered as emphatic, there probably being no other synagogue in any other city in Macedonia. The Jews in different parts had other places of worship called proseuchas. as we have seen, Acts 16:13. At Thessalonica alone they appear to have had a synagogue.