36 Now as they went down the road, they came to some water. And the eunuch said, "See, here is water. What hinders me from being baptized?" 37 Then Philip said, "If you believe with all your heart, you may." And he answered and said, "I believe that Jesus Christ is the Son of God."
Acts 8:36-37
The oldest New Testaments manuscripts do not include verse 37. This verse is routinely cited as proof that only professing believers may be baptized. I doubt any Christians would dispute that—at least when we are speaking of adult baptisms. When the verse is used to say baptism of adults is not biblical, there is a problem. Here is why this verse is not necessary to make the point that as many Christians assert, believer’s baptism is preferable over infant baptism:
First, we must never base doctrine on a narrative passage (the record of what happened), alone. Though the narrative is accurately recorded in the Bible, that doesn’t make it a doctrinal proof text unless a didactic (teaching) passage also affirms the doctrine in question.
Second, the same is doubly true if one is trying to base doctrine on a passage that is questionably not in the oldest manuscripts. (The older the manuscript, the more likely it is more accurate.)
Third, while verse 37 appears to be a great proof-text for believers baptism, it is not needed. The teaching of the New Testament on baptism supports the doctrine (and practice) of baptizing only those who have a credible profession of faith. The reason is that the New Testament clearly teaches that rituals (even biblical rituals like baptism) are only valid if the spiritual basis for the ritual is a reality. For example physical circumcision meant nothing unless one was also circumcised in heart (Romans 2:25-29). The same is true for baptism. In other words, since baptism is a symbol of identifying with Christ and the washing away of sin by His grace, unless one has received Christ and has had his sins washed away by Jesus, the symbol is not only ineffectual, but meaningless.
Here is the biblical order: (1) Get saved by God’s grace alone, received through faith alone, in Christ alone. (2) Get baptized as an outward visible symbol of the inward spiritual reality.