Who was the first person in the Bible to be baptized?
The first recorded baptism in the Bible were the people in Israel going to the Jordan River to be baptized by John the Baptist (Matthew 3:4-5). At least, that is the first group. The first person recorded in the Bible to be water baptized was Jesus of Nazareth (Matthew 3:16).
However, historically the Jews were baptizing any proselyte, a convert to Judaism. It was part of the conversion experience to be water baptized. This may be more John the Baptist got the idea. Although his baptism was not a baptism for conversion.
It is quite possible that the proselyte water baptism idea in Judaism gave way to at least certain rabbis like John the Baptist water baptizing their disciples. Disciples followed the rabbi’s teachings on Scripture.
We know that John had his own disciples because they visited Jesus to ask him if he is the Messiah they have been looking for (Luke 7:18). There might have been an issue between John’s disciples and Jesus’ disciples in the early establishment of the Christian Church.
One example of this is that Paul goes to see the Ephesians in Acts 19 and they have never heard of the baptism into Jesus, only a baptism into John (Acts 19:3-5). It was within Christianity that water baptism became a means for witnessing to others about the change of life in Christ.
Some believe that water baptism is salvation while others teach water baptism is only an effective means of sharing with people what Christ has done in saving you. Within Scripture, most interpreters understand water baptism to be an illustration of death to sin and life in Christ (Romans 6:1-4).
Even within the pages of Acts, most water baptisms occurred only after people wanted to follow Christ. After the Gentiles speak in tongues as the apostles did in Acts 2:1-4, Peter says that they cannot deny water baptism to these converts (Acts 10:44-48).
Even the Ethiopian eunuch is baptized in water following a full understanding of how Christ fulfills Old Testament prophecy, though there is no one other than Philip to witness it (Acts 8:36-38).
There may be a few texts where it is not immediately inferred that water baptism happens after conversion to Christ. This is why today there are two views on water baptism. The first is that it is an act of salvation, believed by Roman Catholics and perhaps a few Protestants. The other view is that it is a witness after the fact of conversion, believed by most Protestants.