Acts 18:4

and persuaded the Jews and the Greeks There are no articles in the original and they are omitted in the Revised Version. No doubt, as in other Gentile cities, the religion of the Jews in Corinth gained the attention of many among the Gentiles, who as proselytes or inclining thereto would form part of the Sabbath audience in the synagogue. According to his rule St Paul addressed himself to the Jews first.