Why did Paul always go to the synagogue first in every city he visited?
Paul went to the synagogue first because Jews were present in every city of importance, and as a Jew steeped in Judaism with love for his kinsmen according to the flesh, he brought the message to them first. He expounded the Old Testament Scriptures, since no New Testament existed yet.
Les explains that because Jews were now in every city of the Roman Empire, wherever the Apostle Paul went he went first to the Jew, to the synagogue, since they were in every city of any import. Being a Jew himself, steeped in Judaism and having a love for his kinsmen according to the flesh, in every city he would go first to the synagogue of the Jew and expound to them out of the Old Testament. Les notes there was no New Testament yet; the Gospels had not been written until after Paul wrote his letters, so he could not tell people to read Matthew, Mark, Luke, and John. Everywhere he went, Paul had to speak the Word verbally because nothing was written until he began his letters.