Acts 18:28

for he mightily convinced the Jews The verb expresses more than is given thus. He brought the objections of the Jews to the test of Scripture and confuted them. The disciples, who had already believed, appear to have been suffering from Jewish gainsayers. It was by his power in the Scriptures that Apollos was helpful against these adversaries of the faith. The Revised Versionhas changed "mightily" into "powerfully" to little profit. Shakespeare says "you have mightily persuaded" (As you Like it, i. 2. 218).

and that publickly By his discourses in the synagogue. This was an important feature in the help that Apollos gave. He was a learned Jew, able to set forth to whole Jewish congregations how their Scriptures were receiving their fulfilment. Thus they who already believed would be strengthened.

shewing by the scriptures that Jesus was the Christ See above, on Acts 18:5. The Jews had complained before Gallio that St Paul's teaching was a religion "contrary to the law." Those who heard Apollos learnt that in Jesus they were accepting the "fulfiller of the law."