Here we have a good explanation by Professor Walter Veith...
Baptism is a symbol of our willingness to accept the Gospel of Jesus Christ. It is a conscious decision and proclamation.
He that believeth and is baptized shall be saved; but he that believeth not shall be damned (Mark 16:16).
Infants cannot make a conscious decision. Therefore, to baptize them defeats the whole purpose of the ceremony. Also, infant baptism is never taught in the Scriptures.
The doctrine of infant baptism is of pagan origin and was brought into the Church by Roman Catholicism. As with most Catholic doctrines, infant baptism has its origins in the Babylonian mysteries....In Babylon, new birth was conferred by baptism of infants. European pagans sprinkled their newborns or immersed them, and to this day the "holy water" used for baptism in some circles is still prepared according to the pagan custom of plunging a torch from the altar into the water. Having introduced infant baptism, the Roman Catholic Church was opposed to adults being baptized and even issued the following decree: "Let him be accursed who says adults must be baptized."
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In Acts 8, the King James Version gives a full description of the baptism of the eunuch. The eunuch was a high official from Ethiopia (
Acts 8:27) and had come to worship in Jerusalem. He was reading the book of Isaiah when Philip was sent to him and explained to him the passages pertaining to the Messiah.
When he had grasped their significance and recognized Jesus Christ in these verses, he was ready to be baptized (
Acts 8:27-35). The KJV continues with the following verses:
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 may.' 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 into the water, both Philip and the eunuch, and he baptized him (Acts 8:36-38).
The question of the eunuch, "What doth hinder me to be baptized?" is answered by Phillip in verse 37:
If thou believeth with all thine heart, thou mayest.
Modern translations leave out verse 37, and the eunuch is thus denied his answer. It is stated in these translations that certain manuscripts do no contain this verse, and therefore the verse should not be included.
However, these modern translations do not do justice to the chiastic structure of the passage in question. The passage is written in question-answer chiasm and leaving out verse 37 would destroy this literary structure.
Omission of the verse is however convenient for those who propagate infant baptism, because the condition for baptism mentioned in this verse 'believing with ones whole heart' cannot be met by infants. Both infant baptism and baptism by pouring have been introduced by Roman Catholicism into the Church, but they find no support in the Scriptures..."
http://amazingdiscoveries.org/S-deception-infant-baptism-believer