There is always an outward manifestation of an inward work that gives God the glory. Repentance is that inward work that changes our heart to seek Gods ways, Baptism is that outward manifestation glorifying God as the one who has done that work within and signifies that we have accepted Him and put off the flesh as He did by death and is a necessary part of salvation, (Acts 2:37,38, Romans 6:3-6).

Baptism is an opportunity to both the one getting baptized and those witnessing the baptism to glorify God as much as it is a witness to the non-believer. Baptism is as much a part of salvation as Speaking in tongues is. The receiving of Gods Spirit is an inward work (indwelling), but tongues is a glorifying (manifesting) of what God has done inward. Both serve to Glorify God and both are equally necessary as a confirmation of the work that has taken place by God within.