Water baptism is the outward testimony or sign of an inward reality of being born again. It means the entry into fellowship with believers through Christ’s death and resurrection symbolized by going under the water and rising out of it. It symbolizes that our old way of living is buried and we now live by Christ’s resurrection life. Obviously it is only for true believers otherwise the symbolism has no meaning!
This outward baptism with water symbolizes the inward washing away of our sins through faith in Christ: “He saved us through the washing of rebirth and renewal by the Holy Spirit” (Titus 3:5). Through faith in Christ the Holy Spirit washes away our sins and imparts the new birth.
Jesus referred to this as being “born of the water and the spirit” (John 3:5). It is not some magical ritual that gives us a relationship with God. It does not impart anything to the recipients. It is a symbol of faith in Jesus Christ that does impart the new birth and the washing away of our sins.