I believe you are referring to the words of John the Baptist in John 1:32-34, “And John bare record, saying, I saw the Spirit descending from heaven like a dove, and it abode upon him.  And I knew him not: but he that sent me to baptize with water, the same said unto me, Upon whom thou shalt see the Spirit descending, and remaining on him, the same is he which baptizeth with the Holy Ghost. And I saw, and bare record that this is the Son of God.”  (This event is also recorded in Matthew 3:11, Mark 1:8, and Luke 3:16).  John’s baptism was a baptism of ‘repentance’ (Matthew 3:11).  To those who came to John to be baptized, he said to them in Luke 3:8, “Bring forth therefore fruits worthy of repentance, and begin not to say within yourselves, We have Abraham to our father: for I say unto you, That God is able of these stones to raise up children unto Abraham.”  He would baptize those who had truly repented of their sins and did not rely upon their heritage as a means of being accepted by the Lord.

Baptism today is not the same as John’s baptism.  The mode of baptism is the same, immersion in water, but the reason is different.  We read in Romans 6:3-6, “Are you ignorant that we, as many as have been baptised unto Christ Jesus, have been baptised unto his death? We have been buried therefore with him by baptism unto death, in order that, even as Christ has been raised up from among the dead by the glory of the Father, so we also should walk in newness of life. For if we are become identified with him in the likeness of his death, so also we shall be of his resurrection; knowing this, that our old man has been crucified with him, that the body of sin might be annulled, that we should no longer serve sin.” (Darby Translation).  This shows us that baptism identifies us as one who believes on the Lord Jesus Christ as his/her savior.  After being saved, the Lord would have us be baptized to show that we have believed on Him as our savior.

We have examples of this in the Bible.  Upon the occasion of Cornelius’ salvation, we read in Acts 10:47, “Can any man forbid water, that these should not be baptized, which have received the Holy Ghost as well as we?”  On the occasion of the Ethiopian eunuch’s salvation we read in Acts 8:35-38, “Then Philip opened his mouth, and began at the same scripture, and preached unto him Jesus. And as they went on their way, they came unto a certain water: and the eunuch said, See, here is water; what doth hinder me to be baptized? And Philip said, If thou believest with all thine heart, thou mayest. And he answered and said, I believe that Jesus Christ is the Son of God. And he commanded the chariot to stand still: and they went down both into the water, both Philip and the eunuch; and he baptized him.”  In both these events, we see that upon accepting the Lord Jesus Christ as their savior, these men were baptized with water.

There is, however, another baptism that occurs at the moment of salvation…the baptism of the Spirit.  We first read of this baptism on the day of Pentecost.  Acts 2:1-4, “And when the day of Pentecost was fully come, they were all with one accord in one place. And suddenly there came a sound from heaven as of a rushing mighty wind, and it filled all the house where they were sitting. And there appeared unto them cloven tongues like as of fire, and it sat upon each of them. And they were all filled with the Holy Ghost, and began to speak with other tongues, as the Spirit gave them utterance.”  It is this baptism of the Spirit that makes us part of the church, the body of Christ, as we read in 1 Corinthians 12:13, “For by one Spirit are we all baptized into one body, whether we be Jews or Gentiles, whether we be bond or free; and have been all made to drink into one Spirit.” Everyone who believes on the Lord Jesus is immediately indwelt by the Holy Spirit and is brought into the body of Christ.  We read in Ephesians 1:13, “In whom ye also trusted, after that ye heard the word of truth, the gospel of your salvation: in whom also after that ye believed, ye were sealed with that holy Spirit of promise.”  (356.6)