This is a difficult passage when we only recognize one type of baptism: in water.
However, Jesus is promised to baptize us with the Holy Spirit and with fire.
"I (this is John the Baptist
) baptize you with water for repentance, but after me will come One more powerful than I, whose sandals I am not worthy to carry. He (this is Christ
) will baptize you with the Holy Spirit and with fire."
The baptism of the Holy Spirit is the baptism of power.
"But you shall receive power when the Holy Spirit has come upon you; and you shall be witnesses to Me in Jerusalem, and in all Judea and Samaria, and to the end of the earth.”
The baptism of fire is suffering so that we might learn obedience.
So let's look at "the dead" for whom some have been baptized with the Holy Spirit (power) and fire (suffering).
1And you (this is the Ephesians)
He made alive, who were dead in trespasses and sins, 2in which you once walked according to the course of this world, according to the prince of the power of the air, the spirit who now works in the sons of disobedience, 3among whom also we all once conducted ourselves in the lusts of our flesh, fulfilling the desires of the flesh and of the mind, and were by nature children of wrath, just as the others.
4But God, who is rich in mercy, because of His great love with which He loved us, 5even when we were dead in trespasses, made us alive together with Christ (by grace you have been saved), 6and raised us up together, and made us sit together in the heavenly places in Christ Jesus, (because this is present tense, this is not about going to heaven but about being received into the same place as the Lord: with power and authority
) 7that in the ages to come He might show the exceeding riches of His grace in His kindness toward us in Christ Jesus. 8For by grace you have been saved through faith, and that not of yourselves; it is the gift of God, 9not of works, lest anyone should boast. 10For we are His workmanship, created in Christ Jesus for good works, which God prepared beforehand that we should walk in them.
Paul understood that the power given to him (baptism of the Holy Spirit) and the suffering he endured (baptism of fire) was for the benefit of those to whom he was sent. His message, properly believed, delivered the dead from the kingdom of darkness and conveyed them into the kingdom of the Son of His love.
He has delivered us from the power of darkness and conveyed us into the kingdom of the Son of His love
Power is required to convey people from one kingdom to another.
Now, this is the next chapter of Ephesians (3):
For this reason I, Paul, the prisoner of Christ Jesus for you Gentiles— 2 if indeed you have heard of the dispensation of the grace of God which was given to me for you (Paul understood that the grace he was given by Christ Jesus was for the benefit of the Ephesians to whom he was sent... who were dead in their sins)
, 3 how that by revelation He made known to me the mystery (as I have briefly written already, 4 by which, when you read, you may understand my knowledge in the mystery of Christ), 5 which in other ages was not made known to the sons of men, as it has now been revealed by the Spirit to His holy apostles and prophets.
Paul was baptized with fire and with the Holy Spirit for the benefit of the dead: i.e. he suffered and received power from Christ not for himself but for the sake of the ones to whom he was sent: he was baptized for the dead.
Let's look at the passage again with a verse that appears prior to:
But now Christ is risen from the dead, and has become the firstfruits of those who have fallen asleep.
Furstfruits is a standard for the harvest. You know much about the harvest by examining the firstfruits. The word also assumes on a continuing harvest, that there are more to come. Now the verse:
Otherwise, what will they do who are baptized for the dead, if the dead do not rise at all?(Paul is saying: what was the value of the power I was given or the things I suffered if the dead do not arise in the likeness of Christ?)
Why then are they baptized for the dead? (Why go through fiery trials and if there is no value?
) 30 And why do we stand in jeopardy every hour? (And, why would anyone put themselves in danger if there is no accompanying promise of life from the Lord?
) 31 I affirm, by the boasting in you which I have in Christ Jesus our Lord, I die daily. 32 If, in the manner of men, I have fought with beasts at Ephesus, what advantage is it to me? If the dead do not rise, “Let us eat and drink, for tomorrow we die!” (In the last sentence he is speaking like a fool to make a point: we might as well party if there is no point to any of what I am to you in Christ
)
Perhaps this provided some light.