In Matthew 3:11, John the Baptist says, "I baptize you with water for repentance, but one who is more powerful than I is coming after me; I am not worthy to carry his sandals. He will baptize you with the Holy Spirit and fire" (NRSV).
What did Jesus do that John the Baptist did not? John's baptism already removed sins, so why was Jesus' work even necessary? John implied that his own ministry was inadequate when he differentiated his work of water baptism from Jesus' baptism with the Holy Spirit. So what is the baptism of the Holy Spirit?
Here are three proposals:
1. My personal favorite goes like this: John baptized people with water, which brought about God's forgiveness of their sins. But something was missing. John could get them wet, but they still walked away as sinners. Their carnal minds remained at enmity against God. They needed the Holy Spirit to change.
I realize that I'm reading Paul into Matthew, which is not the best approach, since I want Matthew to explain himself rather than forcing him into another author's mold. But Paul stresses that the flesh is sinful, and he states that the Holy Spirit is necessary for one to defeat the flesh and bear spiritual fruit, including love, joy, peace, patience, goodness, kindness, and generosity (Romans 6-8; Galatians 5). Could that be what John means when he contrasts inadequate water baptism with the baptism of the Holy Spirit?
The Hebrew Bible also discusses the Holy Spirit's role in making people internally righteous, and John the Baptist as well as Matthew were most likely familiar with that theme. Ezekiel 36:27 says, "I will put my spirit within you, and make you follow my statutes and be careful to observe my ordinances."
And the Dead Sea Scrolls seem to present something similar. Community Rule (1QS) 3:6-12 talks about the Holy Spirit cleansing the initiate of injustice, while the water purifies the flesh. Is the Community Rule implying that water is not enough to cleanse the initiate, who needs the extra "umph" of the Holy Spirit?
As far as Matthew's message is concerned, Matthew 1:21 says that Jesus will save his people from their sins. Perhaps Matthew thinks that Jesus will do so through the baptism of the Holy Spirit, which makes sinners internally righteous.
2. In the Hebrew prophets, the Holy Spirit is a significant aspect of Israel's end-times restoration. When God pours out his Spirit upon Israel, she thrives and experiences God's intimate presence. Isaiah 44:3-4 states:
"For I will pour water on the thirsty land, and streams on the dry ground; I will pour my spirit upon your descendants, and my blessing on your offspring. They shall spring up like a green tamarisk, like willows by flowing streams."
Ezekiel 39:29 has, "I will never again hide my face from them, when I pour out my spirit upon the house of Israel, says the Lord GOD."
By contrast, the prophets often present an unquenchable fire as an instrument of God's judgment (Isaiah 33:14; 66:24; Jeremiah 17:27; Ezekiel 20:47). Remember: John said that the coming one would baptize with the Holy Spirit and with fire.
So perhaps John was saying this: "I baptize with water, but that's so you'll be prepared for the truly powerful person, the Messiah to come. He will immerse Israel with the Holy Spirit as he restores her and brings her blessing. But the wicked he will destroy with unquenchable fire. So make sure you're righteous. Repent!"
3. The Book of Acts offers its own interpretation of John's statement. For the author of Luke-Acts, Jesus baptized the Jews with the Holy Spirit at Pentecost, and he also did so to the Gentiles who were with Cornelius (Acts 1:4-5; 11:16-17). In the Book of Acts, the Holy Spirit brings joy (13:52), praise (10:46), comfort (9:31), guidance (8:28; 13:2; 16:7), and power for the Christian mission (1:8). It is responsible for certain gifts in the church, such as prophecy (11:29). It's often accompanied by a visible manifestation, mainly tongues (Acts 2:3; 10:46; 19:6). In Acts 8, the church leaders could somehow tell that the baptized people from Samaria had not yet received the Holy Spirit. And, when they did receive it, Simon the sorcerer saw something impressive, since he tried to purchase the ability to give it. And so the reception of the Spirit must have been identifiable in some way.
And here is where I struggle. Does that mean I have to speak in tongues to be saved? There are a lot of charismatics who would answer "no" to that question. Their reason is John 20:22, in which Jesus breathes on his disciples and tells them to receive the Holy Spirit. According to many charismatics, the disciples initially received the Holy Spirit in John 20:22, which led to their entry into the Body of Christ and their status as children of God (Romans 8:9-16; I Corinthians 12:13). In Acts 2, however, the Holy Spirit empowered them for ministry. For a lot of charismatics, every Christian receives the Holy Spirit at salvation, but there is a "second baptism" that God graciously gives to some Christians. This baptism includes greater closeness to God, joy, peace, and empowerment for Christian service. And tongues are the sign that it has occurred.
But the charismatic scenario doesn't really convince me, for the Book of Acts does not mention a second baptism. Acts 8 says that the Samarian converts received the Holy Spirit when Peter and John prayed for them (Acts 8:14ff.). And, as I said, the gift of the Holy Spirit in Acts 8 had to be identifiable in some way, through tongues, miracles, or other indications. John 20:22 and the Book of Acts may have different traditions about when the disciples first received the Holy Spirit.
In my opinion, if tongues are a requirement for salvation, then that is pretty low of God. There are many people who seek God but do not have the gift of tongues. If tongues are a necessary indication of the Holy Spirit's presence, then God's unwillingness to give such seekers his Spirit is pretty callous. And that would not make sense in light of Luke 11:11-13:
"Is there anyone among you who, if your child asks for a fish, will give a snake instead of a fish? Or if the child asks for an egg, will give a scorpion? If you then, who are evil, know how to give good gifts to your children, how much more will the heavenly Father give the Holy Spirit to those who ask him!"
According to this passage, God is generous with his Spirit, not stingy.
But how does this relate to John the Baptist? If number 3 is correct, then John could be saying this: "Look, I'm getting you wet, and that's leading to your forgiveness, which is well and good. But do you want to experience the presence, fullness, and power of the living God in a way that you never have before? Then wait for the one who will immerse you in the Holy Spirit. Purify yourself, for he is coming soon! You Jews who repent will experience God in this profound way. The rest of you will perish when the Romans destroy Jerusalem. The choice is yours."