The verse below explains the relationship of baptism to salvation in Biblical Christianity:
“and this water symbolizes baptism that now saves you also—not the removal of dirt from the body but the pledge of a clear conscience toward God.” (I Peter 3:21 NIV)
The Apostle Peter is saying here that the Genesis flood is representative of baptism. Just as Noah and his family were raised above the waters of death in the ark, so true Christians have been raised above the waters of eternal death through the promise of an eternal resurrection.
The apostle Peter is clear here that the physical act of baptism–being immersed in water–does not save us. Rather we are saved by “the pledge of a clear conscience toward God.” This means that we are saved not by going through some physical ritual, but rather by having a change of heart.
The physical act of baptism is supposed to be done only to those who genuinely believe. Every true Christian is commanded to be baptized, and when we obey that commandment willingly we are “pledging” ourselves to follow God. The physical act of baptism is a picture of the change that has overcome us. Physically we are immersed completely in water and raised back up above the surface again. It is as if we had died and come back to life. This is a picture that we have died to sin and are now raised anew in life in Christ. We have left behind spiritual death for spiritual life.
Some people think that the physical act of baptism being performed by a specially ordained priest is what makes you saved. It is not! Hundreds of Bible verses make it clear that salvation comes through faith and repentance. Physical baptism is a statement that this change has occurred in your heart. Every true believer will want to be physically baptized. Those who die unexpectedly before their baptism are still saved.