I thank God that I baptized none of you except Crispus and Gaius, so that no one can say you were baptized in my name. I did, in fact, baptize the household of Stephanas; beyond that, I don’t recall if I baptized anyone else. For Christ did not send me to baptize, but to preach the gospel—not with eloquent wisdom, so that the cross of Christ will not be emptied of its effect.
The popular notion that conversion necessarily precedes baptism and should be seen as a seal or testimony or even a confession to conversion and commitment previously made is nowhere clearly stated in the New Testament.
(Ben Witherington: Troubled Waters: The Real New Testament Theology of Baptism; p. 111)
I’ve written three articles on water baptism: