What does Acts 18:7 mean?

Paul shares the message of Jesus' offer of forgiveness to the Jews in the synagogue of Corinth, but not many believe him. He is frustrated because the Messiah is for the Jews. The Jews as a whole people should realize how Jesus of Nazareth is the Messiah promised in the Hebrew Scriptures. They should join Paul in presenting Jesus to the whole world: the blessing of Abraham (Genesis 12:3). Crispus, the ruler of the synagogue, and his whole family follow the call (Acts 18:8). Paul also cares about the Jews as a whole (Romans 9:1–5). He can't force them, however, and when the synagogue leadership seems on the verge of expelling him , he proclaims he has fulfilled his responsibility and God will hold them accountable for their choice (Acts 18:6).

Titius Justus, as a "worshiper of God," is a Gentile. There are three classes of people who worship the Jewish God. Jews are, obviously, the first. The second is proselytes—Gentiles who fully convert to Judaism, the males accepting circumcision. Third are the "God-fearers" or "God-worshipers"—Gentiles who follow God and go to synagogue but do not fully convert. The book of Galatians is largely about how Gentile Christians do not have to first become Jews.

This is not the last time Paul will find a long-term solution to his expulsion from the synagogue. During his third missionary journey, he will travel to Ephesus and wind up in the hall of Tyrannus for two years (Acts 19:9–10). If God wants us to minister, He will make a way.