Adam Clarke on Acts 18:4

He reasoned in the synagogue every Sabbath - Discoursed at large concerning Jesus as the Messiah, proving this point from their own Scriptures, collated with the facts of our Lord's life, etc.

And persuaded the Jews and the Greeks - Many, both Jews and proselytes, were convinced of the truth of his doctrine. Among his converts was Epenetus, the first fruit of his labor in Achaia, Rom 16:5; and the family of Stephanas was the next; and then Crispus and Caius, or Gaius; all of whom the apostle himself baptized, 1Cor 1:14-16. See on Act 18:8 (note).