How did Apollos convince the Jews that Jesus was the Christ?
Apollos mightily convinced the Jews publicly by showing from the Old Testament Scriptures that Jesus of Nazareth was indeed the Christ. He could also continue with Paul's gospel—that Christ died for the sins of the world, was buried, and arose from the dead.
Les explains that Apollos had already been effective, but after receiving additional knowledge and information that began with Paul and came through this other Jewish couple, he mightily convinced the Jews. He did it publicly, not in a corner, showing by the Old Testament Scriptures that Jesus of Nazareth was indeed the Christ. Les notes Apollos could go beyond that to the grace mentioned in verse 27 and continue with Paul's gospel—that Christ died for the sins of the world, was buried, and rose from the dead. That fuller revelation shows the difference between identifying the Old Testament Messiah and proclaiming Paul's gospel. Les applies this by saying it took two common, ordinary people to bring Apollos to further revelation, and that is where believers come in: humbly, not with pride or sarcasm, use the Book skillfully to show others what they are missing.