Baptism Is a Symbolic Ordinance Representing Death and Resurrection
Doctrine and Covenants 128:12–13
12 Herein is glory and honor, and immortality and eternal life—The ordinance of baptism by water, to be immersed therein in order to answer to the likeness of the dead, that one principle might accord with the other; to be immersed in the water and come forth out of the water is in the likeness of the resurrection of the dead in coming forth out of their graves; hence, this ordinance was instituted to form a relationship with the ordinance of baptism for the dead, being in likeness of the dead.
13 Consequently, the baptismal font was instituted as a similitude of the grave, and was commanded to be in a place underneath where the living are wont to assemble, to show forth the living and the dead, and that all things may have their likeness, and that they may accord one with another—that which is earthly conforming to that which is heavenly, as Paul hath declared, 1 Corinthians 15:46, 47, and 48 . . .
President Joseph Fielding Smith wrote:
“The Lord has placed the baptismal font in our temples below the foundation, or the surface of the earth. This is symbolical, since the dead are in their graves, and we are working for the dead when we are baptized for them. Moreover, baptism is also symbolical of death and the resurrection; in fact, [it] is virtually a resurrection from the life of sin, or from spiritual death, to the life of spiritual life (see D&C 29:41–45). Therefore when the dead have had this ordinance performed in their behalf they are considered to have been brought back into the presence of God, just as this doctrine is applied to the living.”
(Church History and Modern Revelation, 2 vols. , 2:332.)