The historical and Biblical record on the purpose of water baptism is remarkably clear and simple.
An excellent example of the clarity was a comment I read in a book by David Bercot titled Will the Real Heretics Please Stand Up. Bercot noted that most Evangelicals do not believe that John 3:5 is a reference to baptism. John 3:5 says that unless a person is “born of water and the Spirit” he cannot see the kingdom of God.
Since Evangelicals generally believe that water baptism is a public testimony having nothing to do with salvation, they usually see the water in that verse as referring to our physical birth. 
Bercot’s comment on this is notable.
“If Jesus,” he says, “didn’t mean water baptism in this verse, then he is a terrible communicator because everyone without exception for the next 1600 years thought he did.” 1
As I have studied on this topic, I have been surprised to see that this was not even an issue that was debated by the early church. From the earliest centuries it was believed that John 3:5 was a verse on the regeneration that God gives the believer at baptism. I wrote an article a while back touching on the teachings of the early church fathers on baptism. You can see that article by going here.
Another interesting point I have learned is if someone came about teaching that baptism wasn’t essential to salvation, it was considered heresy
In 140-230 AD, Tertullian wrote, “Happy is our sacrament of water, in that, by washing away the sins of our early blindness, we are set free and admitted into eternal life! A treatise on this matter will not be superfluous; instructing not only such as are just becoming formed in the faith… The consequence is, that a viper of the Cainite heresy, lately conversant in this quarter, has carried away a great number with her most venomous doctrine, making it her first aim to destroy baptism. Which is quite in accordance with nature; for vipers and asps and serpents themselves generally do affect arid and waterless places.”
So the question must be raised, “If the early church leaders that were nearest to the time of the Apostles taught this doctrine, what does this mean for popular teaching today on baptism? Is it heresy, or not? Let me know your thoughts.
1. David W., Bercot. Will the Real Heretics Please Stand Up. 3rd Ed. Amberson, PA: Scroll Pub Co, 1999. Print.
2. Tertullian. On Baptism, Ante-Nicene Fathers, vol. 3, pg. 669.


