My position regarding Acts 19 is that it is talking about Old Testament saints.
John the Baptist baptized Jews. This was not a Christian baptism, but was a baptism that demonstrated the Jews themselves needed spiritual cleansing. Many Jews thought that they were righteous by virtue of being a descendant of Abraham.
The reality is that they were not spiritually cleansed. And, regarding salvation, they didn't even know that Jesus was the Messiah to die for their sins at this point. Baptism is actually identification with Jesus, and they didn't even know he was their Savior. Read Romans 6:1-14.
I don't think they believed at John's baptism in the same sense as Christian belief, because they did not know Jesus was Messiah. They were an Old Testament saint, and were saved, but they were not identified with Christ yet.
With this baptism, they became identified with Christ and were given the Holy Spirit.
The theme of the book of Acts relates to Acts 1:8. The gospel was to go out of Jerusalem, and reach various people groups. Speaking in languages (I won't use the word tongues because I think it's an ignorant translation) accompanied receipt of the Holy Spirit. Laying on of hands accompanied baptism, and a manifestation of the Holy Spirit occurred at the same time.
Various subgroups within the early church are recognized throughout the narrative.
Jews
Samaritans
God-fearers
Ordinary, non-God fearing Gentiles
Old Testament saints
This shows a fulfillment of Acts 1:8.
I will provide a few commentaries (and for those who don't like me providing external information, TOUGH):
Acts 1:8 1:8 This is both the general outline and central theme of Acts. The gospel will proceed from Jerusalem (chs. 1–7), to Judea and Samaria (chs. 8–12), and to the ends of the earth (chs. 13–28). Thematically, the disciples’ role is to be Jesus’ “witnesses.” Their power is the Holy Spirit. Their task is to take this message from “Jerusalem . . . to the ends of the earth.” This movement is both geographic (from Jerusalem to Rome) and ethnic (from Jews to Gentiles). The movement also continues what started in Luke’s Gospel. While the great central section of Luke’s Gospel describes Jesus’ journey to Jerusalem to accomplish God’s salvation (Luke 9–19), Acts describes the outward movement from Jerusalem to proclaim God’s salvation everywhere.
(NIV Biblical Theology Study Bible)
Acts 1:8 Verse 8 is the thematic statement for all of Acts. It begins with the Spirit's power that stands behind and drives the witness to Jesus. Then it provides a rough outline of the book: Jerusalem (chs. 1-7), Judea and Samaria (chs. 8-12), and the end of the earth (chs. 13-28).
(ESV SB Notes)
Acts 1:8 my witnesses in Jerusalem and in all Judea and Samaria, and to the end of the earth. Jesus’ words forecast the geographical expansion of the church narrated in the book of Acts. The Jerusalem witness (ch. 2) gives in miniature form God’s worldwide ministry: “Jews . . . from every nation” (2:5) and Gentile proselytes (v. 11) who hear and believe carry the message far and wide. In the rest of Acts, the gospel spreads throughout Jerusalem (3:1-8:1), then to Judea and Samaria, including Antioch of Syria (8:1-12:25), and finally to the ends of the earth (13:1-28:31). Recall that Acts 1:8 is an outline for the entire book (see the Introduction to Acts: Literary Features).
(Reformation SB)
Specifically regarding Acts 19:1-6, I will add these notes, which I think are accurate:
Acts 19:1-6 19:1 disciples. Either believers in Jesus (like Apollos, 18:25) or followers of John the Baptist. The latter is perhaps more likely because they have not yet received the Spirit. In either case, they have insufficient knowledge of Jesus as the Messiah and do not know about the pouring out of the Spirit on the day of Pentecost (v. 2; 2:14–39).
19:4 John’s baptism was a baptism of repentance. It prepared for the coming of the Messiah (10:37; 13:24–25; Luke 3:3, 8, 16).
19:5 baptized in the name of the Lord Jesus. Qualitatively different from John’s baptism of repentance; it symbolizes the regenerating work of the Spirit through the death and resurrection of Christ and entering the new age of salvation.
19:6 placed his hands on them. For the laying on of hands to receive the Spirit, see 8:15–17. tongues. Accompanies the bestowal of the Spirit at Pentecost (2:4, 11) and at the home of Cornelius (10:46), but not in every case of conversion in Acts (8:17). The book of Acts covers a period of transition, and there is no single model or pattern for the coming of the Spirit or its accompanying signs. The general pattern, however, is reception of the Spirit at the time of conversion.
(NIV Biblical Theology Study Bible)
And, again, for those who scoff at me for using study bibles, I really don't care what you think on this. Somehow you think that your opinion based on your professed independent reading should be the only thing that is discussed. I find great value in presenting the educated opinions of scholars such as DA Carson or Wayne Grudem or any other number of brothers in Christ, who have a good knowledge of the Bible, church history, and original languages.
So..on one end of the spectrum I have ME. I am an untrained, fallible man. In the middle, I have YOU. I don't even know your background, but you likely have worse training than me, and even the ones that profess seminary training may be lying. To the far right, I have published, sound, conservative teachers. And, over all, I have God and the Holy Spirit leading me and hopefully you and them too.
I really dislike it when some people discount conscientious brothers in Christ who have dedicated their lives to studying and teaching. I dislike it A LOT.
By the way, I'm not addressing you, wattie..I doubt you hold that view...I just find that when I quote study bibles some get contentious with me on this
Additionally, for those who don't know this, OliveTree has a wonderful, reasonably priced application for both PC and cell phone that displays your preferred text, side by side with your preferred study bible notes. You can change the notes or text at will.
I love this application. Logos has something that is similar, but it is more expensive.
I built up my collection of study Bibles while I was in the hospital with a broken neck, back, and hip. Thank God, I had the resources to spend on this. I couldn't even read a book easily with the broken neck, as I had a halo device installed that held my head onto my shoulders
This was such a blessing to me and I thank God that he provided me with a great Iphone and these tools. I could talk to some of my Christian friends online, do some study, and listen to great Christian music under conditions most would find unbearable. I really recommend developing such tools in case you ever wind up in the hospital or nursing home.