This answer is based on the Christian theology of Emanuel Swedenborg (1688-1772), and his spiritual mode of interpreting the Bible. It represents the view on this subject of the "New Church" or "Swedenborgian" denominations that accept Swedenborg's theology.
The question is based on Luke 3:16-17:
John answered all of them by saying, "I baptize you with water; but one who is more powerful than I is coming; I am not worthy to untie the thong of his sandals. He will baptize you with the Holy Spirit and fire. His winnowing fork is in his hand, to clear his threshing floor and to gather the wheat into his granary; but the chaff he will burn with unquenchable fire."
There are four key elements here related to the question that need to be explained and understood:
- Baptism
- Baptism with water
- Baptism with the Holy Spirit
- Baptism with fire
Baptism
In the New Testament, baptism was practiced by John the Baptist and Jesus' disciples, and commanded by Jesus himself (see Matthew 28:16-20) as a permanent ritual, or sacrament, that would introduce people into the Christian church. Those who are baptized are considered Christians, whether baptized as infants or as adults.
Baptism itself is a ritual of cleansing. As originally practiced, it involved being fully immersed in flowing water such as the Jordan River.
In non-religious terms, baptism is a bath. The purpose of a bath physically is to clean the body of dirt and impurities.
Spiritually, therefore, baptism represents the cleansing of a person from evil, falsity, and sin. This is the first step in the process of being born again, or spiritual rebirth.
That is why baptism is presented in the New Testament as "the baptism of repentance for the forgiveness of sins" (see Matthew 3:11; Mark 1:4; Luke 3:3; Acts 2:38, 13:24, 19:4). Baptism is not about mere physical cleansing; it is a ritual symbolic of the spiritual cleansing of repentance from our sins, and thereby accepting God's forgiveness, entering into the Christian religion, and being born again as a new creation in Christ (see 2 Corinthians 5:17).
In Christianity, baptism takes the place of all the Old Testament rituals of washing and purification.
Luke 3:16 and Matthew 3:11 speak of three forms of baptism:
- with water
- with the Holy Spirit
- with fire
Since baptism in general represents a cleansing of Christian believers from evil, falsity, and sin, each of these forms of baptism represent a cleansing at a different level of a Christian's life.
Baptism with water
In Matthew 3:11, John the Baptist says:
I baptize you with water for repentance.
In the Bible, water is often used as a symbol of truth. For example, Deuteronomy 32:2 reads:
May my teaching drop like the rain,
my speech condense like the dew;
like gentle rain on grass,
like showers on new growth.
Baptism with water, then, represents allowing our lives to be cleansed by the truth of Jesus' teaching.
But more specifically, the baptism of water performed by John the Baptist was a baptism of repentance from evil, falsity, and sin in a person's outward behavior.
When the people being baptized by John asked him what they must do, he told them that they must stop acting wrongly, and start acting rightly:
"What should we do then?" the crowd asked.
John answered, "Anyone who has two shirts should share with the one who has none, and anyone who has food should do the same."
Even tax collectors came to be baptized. "Teacher," they asked, "what should we do?"
"Don't collect any more than you are required to," he told them.
Then some soldiers asked him, "And what should we do?"
He replied, "Don't extort money and don't accuse people falsely—be content with your pay." (Luke 3:10-14)
In fact, John's imprisonment and later execution by Herod was a result of his rebuking Herod for his behavior:
But when John rebuked Herod the tetrarch because of his marriage to Herodias, his brother's wife, and all the other evil things he had done, Herod added this to them all: He locked John up in prison. (Luke 3:19-20)
The first baptism, then, baptism by water, represents the cleansing of our outward actions, and our speech, from evil, falsity, and sin.
The first step in Christian life and rebirth is to stop speaking falsehoods and lies, and stop doing things that are evil and sinful. This is the "baptism of water for repentance" practiced by John the Baptist and by the disciples of Jesus.
But there are two further, and deeper, forms of baptism. John the Baptist said that Jesus Christ (the "one more powerful than I" who "is coming") "will baptize you with the Holy Spirit and fire."
Baptism with the Holy Spirit
The Holy Spirit, like water, refers to truth. But it is truth of a deeper kind. It is not outward truth, but "the spirit of truth":
When the Spirit of truth comes, he will guide you into all the truth; for he will not speak on his own, but will speak whatever he hears, and he will declare to you the things that are to come. (John 16:13, and see also John 14:16-17, 15:26)
Baptism with the Holy Spirit, then, is the next step beyond the cleansing of our outward life through repenting from sin and instead speaking and acting with kindness and truth. Baptism with the Holy Spirit is the cleansing of our inward self, and specifically of our thoughts and beliefs.
The truth that does this is not the outward truth of right behavior represented by the baptism of water performed by John the Baptist, but the deeper spiritual and divine truth that cleanses our mind and spirit from falsity and error.
When we are baptized with the Holy Spirit, we follow the guidance of the Holy Spirit into all the truth. We allow the Holy Spirit to re-form our thinking, our faith, our beliefs. The result of baptism with the Holy Spirit is that our mind is enlightened, and we walk in the light of God's spiritual truth.
Baptism with fire
The third and final form of baptism mentioned in Matthew 3:11 and Luke 3:16 is baptism with fire.
Since ancient times, in all cultures, fire with its warmth has been seen as a symbol of love. In the ancient love poem called "The Song of Solomon," 8:6, we read:
Set me as a seal upon your heart,
as a seal upon your arm;
for love is strong as death,
passion fierce as the grave.
Its flashes are flashes of fire,
a raging flame.
And when Solomon dedicated the first temple, and the people saw fire from the Lord descending over it, they instinctively recognized that it represented the Lord's love for them:
When all the people of Israel saw the fire come down and the glory of the Lord on the temple, they bowed down on the pavement with their faces to the ground, and worshiped and gave thanks to the Lord, saying, "For he is good, for his steadfast love endures forever." (2 Chronicles 7:3, italics added)
When Jesus Christ baptizes us with the Holy Spirit, it is a baptism with spiritual and divine truth.
When Jesus Christ baptizes us with fire, it is a baptism with spiritual and divine love.
Having had our outward behavior cleansed with the baptism of water, and our mind cleansed with the spirit of truth, the third baptism is to have our heart cleansed with the baptism of the fire of God's love.
We humans are a mixture of good and evil loves and motives. Some of the things we want are good. We may enjoy doing a kind deed for a fellow human being in need. But some of the things we want are bad. We may enjoy cussing out someone who has crossed us.
Perhaps through the power of Christ working in our lives we have been able to reform our behavior so that we no longer cuss people out, lie, steal, and so on. Perhaps we even know in our mind that these things are wrong, and we therefore discipline ourselves not to act on them even when we desperately want to.
In the final baptism, the baptism with fire, Jesus Christ cleanses our hearts, meaning our loves, desires, and motives, so that we no longer even want those evil things. We no longer have those evil and selfish impulses. Or if we ever do, instead of feeling the old pleasure at the thought of slugging someone who's insulted us, we find the very thought of doing such a thing intensely distressing and unpleasant.
Baptism with fire is the cleansing of our loves, desires, and motives from all evil, selfish, and greedy impulses, and from the pleasure we used to get from nursing and indulging in those evil desires.
The intense process of purification by fire
This does not happen easily.
It is no accident that "trial by fire" is a process of intense heat, the burning off of chaff, and the purging of dross from metal ores in the process of refining them with intense heat:
His winnowing fork is in his hand, to clear his threshing floor and to gather the wheat into his granary; but the chaff he will burn with unquenchable fire. (Luke 3:17)
And:
See, I am sending my messenger to prepare the way before me, and the Lord whom you seek will suddenly come to his temple. The messenger of the covenant in whom you delight—indeed, he is coming, says the Lord of hosts. But who can endure the day of his coming, and who can stand when he appears? For he is like a refiner's fire and like fullers' soap; he will sit as a refiner and purifier of silver, and he will purify the descendants of Levi and refine them like gold and silver, until they present offerings to the Lord in righteousness. (Malachi 3:1-3)
This cleansing of the heart in the fire of divine love does not happen without the burning off of all our selfish and greedy thoughts and desires in the heated crucible of hard life experience.
As those selfish and greedy thoughts of ours force their way out into harsh words and wrong actions, the impure parts of ourselves are incinerated by "burning coals being heaped upon us" (see Proverbs 25:21-22; Romans 12:19-21), meaning the knowledge and awareness of our own selfishness and greed, and the painful experience of the terribly destructive words and actions that they lead us to say and do.
As we experience these things, the evil desires of our hearts are purged from us, until we no longer have any desire to say and do those evil and destructive things, and take no pleasure in them whatever, but find them horrifying and disgusting.
This is the "baptism with fire" with which Jesus will baptize us if we follow him to the end, fighting the good fight, finishing the race, and keeping the faith (2 Timothy 4:7).
Summary
As we go through this full process of being born again by being baptized with water, the Holy Spirit, and fire, Jesus Christ cleanses our actions, our thoughts, and our desires. In other words, he cleanses us completely, from head to toe and from the outside in.
This process continues throughout our lifetime here on earth. And since even "the heavens are not clean in God's sight" (Job 15:15), we continue to be purified and perfected in heaven to all eternity.
The compact answer to the question, then, covering all three forms of baptism, is this:
- Baptism with water is the cleansing of our outward speech and behavior from evil actions and lies.
- Baptism with the Holy Spirit is the cleansing of our mind and spirit from falsity and error.
- Baptism with fire is the cleansing of our heart from evil impulses and desires, and from the pleasure we used to derive from them.