Most Bible readers assume that Apollos was re-baptized as a part of being taught the way of God more adequately by Priscilla and Aquila. Let’s begin by reading the end of Acts 18 and the beginning of Acts 19.
24 Meanwhile a Jew named Apollos, a native of Alexandria, came to Ephesus. He was a learned man, with a thorough knowledge of the Scriptures. 25 He had been instructed in the way of the Lord, and he spoke with great fervor and taught about Jesus accurately, though he knew only the baptism of John. 26 He began to speak boldly in the synagogue. When Priscilla and Aquila heard him, they invited him to their home and explained to him the way of God more adequately. 27 When Apollos wanted to go to Achaia, the brothers encouraged him and wrote to the disciples there to welcome him. On arriving, he was a great help to those who by grace had believed. 28 For he vigorously refuted the Jews in public debate, proving from the Scriptures that Jesus was the Christ. (Acts 18:24-28)
1 While Apollos was at Corinth, Paul took the road through the interior and arrived at Ephesus. There he found some disciples 2 and asked them, “Did you receive the Holy Spirit when you believed?” They answered, “No, we have not even heard that there is a Holy Spirit.” 3 So Paul asked, “Then what baptism did you receive?” “John’s baptism,” they replied. 4 Paul said, “John’s baptism was a baptism of repentance. He told the people to believe in the one coming after him, that is, in Jesus.” 5 On hearing this, they were baptized into the name of the Lord Jesus. (Acts 19:1-5)
In spite of the normal assumptions, much discussion has occurred about whether Apollos was in fact baptized at this point. The text does not say so, nor does it say anything more generally that would necessarily imply it. A related question is whether the apostles or even the 120 in Acts 1 and Acts 2 were re-baptized. If they had come into a saved relationship during the ministry of Christ (and they had – John 15:3), then his dying would not have made them become unsaved. John’s baptism was for the forgiveness of sins (Mark 1:4), called in Acts 19:4 a “baptism of repentance” which had to be followed by belief in Jesus. Since the Israelites were born into a covenant relationship with God, the forgiveness through John’s baptism was not the forgiveness of initial salvation, but rather the forgiveness of repentance for those in the covenant, much like prayers on the part of Christians accomplish today (1 John 1:9).
My opinion is that those who had experienced John’s baptism before Christ died and maintained faith in him were not re-baptized. I don’t think the 3,000 baptized on the Day of Pentecost included the apostles. If the principle is true that those receiving John’s baptism before the cross and remained faithful would not need a re-baptism, then Apollos would not have needed another baptism. However, John’s baptism would have been invalid if experienced after the cross, for it was superseded by Great Commission baptism, and that was likely the case of those described in Acts 19:1-5. The probable scenario is that Apollos was baptized with John’s baptism before the cross, but then taught and baptized the dozen men in Ephesus with John’s baptism after the cross, which was no longer valid. Hence, Paul re-baptized them with the baptism of the Great Commission. The whole issue is mostly a moot point, for it cannot be applied in any way to those living today. Even if John’s baptism remained valid for men who were baptized before the cross and who maintained faith in Jesus, no such person is alive today! Therefore, while such discussions may be interesting, they tend to produce more heat than light, and have no direct application today. However, in the interest of honest inquiry, I am glad to provide the answer that seems to me most likely correct.