Albert Barnes on Acts 18:28

For he mightily convinced the Jews. He did it by strong arguments; he bore down all opposition, and effectually silenced them. And that publicly. In his public preaching in the synagogue and elsewhere.

Showing by the Scriptures. Proving from the Old Testament. Showing that Jesus of Nazareth corresponded with the account of the Messiah given by the prophets. Jn 5:39.

That Jesus was Christ. See the margin. That Jesus of Nazareth was the Messiah.

(*) "convinced" "earnestly confuted" (c) "by the Scriptures" Jn 5:39 (1) "Jesus was Christ" "is the Christ" Acts 18:5