The prophet of whom Nephi has spoken was John the Baptist. He had seen him in a vision baptizing the Lamb of God (1 Nephi 11:27). Lehi had also prophesied of John (1 Nephi 10:7–10). Nephi’s reference to John at this time is to set the stage for explaining the purpose or doctrine of Christ’s baptism. The reference to the Lamb of God who should take away the sins of the world is speaking of Jesus as a person, not of his baptism.
Nephi gives three reasons for the Lamb of God being baptized. The first was to fulfill all righteousness (v. 5). The plan presented in the pre-mortal council for God’s spirit children to come to earth was to “prove them herewith, to see if they will do all things whatsoever the Lord their God shall command them” (Abraham 3:25). As “the Firstborn” spirit Son of God (D&C 93:21) he was to keep the commandments of the Father. Thus he was baptized as a witness to the Father, or a covenant, that he would be obedient to his commandments or follow the righteous plan of salvation (v. 7). Baptism is a covenant between God and man.
The second reason for Jesus being baptized was for a witness of the Holy Ghost. Baptism was a commandment, or a prerequisite, for receiving the Holy Ghost. The Holy Ghost descended upon Jesus after he was baptized (v. 8). The form of a dove should be translated as “the sign of the dove” according to the Prophet Joseph Smith. “The sign of the dove was instituted before the creation of the world, a witness for the Holy Ghost, and the devil cannot come in the sign of the dove.” The sign was given to John to signify the truth of the deed” (TPJS, 276 and Facsimile No. 2, Figure 7 in the Book of Abraham in the Pearl of Great Price). Although the Holy Ghost itself may have been seen by some (see Luke 3:22), it seems that an actual dove was also present as a witness to those who were not spiritually ready to see the Holy Ghost, but were capable of recognizing the significance of the sign of the dove.
The third reason for Jesus being baptized was for an example to the children of men (v. 9). Baptism is the gate to the path to eternal life as will be shown later. Jesus demonstrated the strictness of the path and the narrowness of the gate by which one enters the path. Strait means narrow and restricted. The straitness of the path shows the restrictions that are placed on a person to get to the gate. The narrowness of the gate shows the inflexible or limited entrances to the path. The gate is baptism (v. 17) and the strait path to baptism is repentance. Therefore the example set by Christ to be baptized shows it is important to repent of the violations of the commandments required to be baptized and to accept the proper mode of baptism. These actions help one to enter into the path that leads to eternal life. That path on earth is the Church of Jesus Christ. Therefore we take upon us the name of Christ by baptism.
In light of these three reasons for Christ’s baptism. Nephi gives three reasons for us to be baptized. The first reason is because we are unholy and need to be baptized for a remission of our sins (v. 5). The second reason is to witness to the Father that we are willing to keep his commandments (v. 10). Nephi also adds that we witness to the Father that we are willing to take upon us the name of Christ at this time. Our taking his name could be counted as another reason, but Nephi seems to make it a part of our witness to keep the commandments
(v. 13). The Book of Mormon later explains that we “have entered into a covenant with [God]” through this witness (Mosiah 18:10, 13). The third reason comes from the voice of the Son declaring that the Father will give the Holy Ghost to those that are baptized (v. 12). Nephi then summarizes and emphasizes that we must enter into this covenant of baptism with full purpose of heart, without hypocrisy or deceit (v. 13). He implores the children of men to follow the Savior and receive the baptism of fire and of the Holy Ghost as the Father had commanded in the righteous plan of salvation. Those who receive the baptism of fire and the Holy Ghost will be able to speak with the tongue of angels and shout praises to the Holy One of Israel (v. 13). The voice of the Son came again unto him saying that after entering into the covenant of baptism and receiving the baptism of fire and the Holy Ghost, if the covenant was not kept, it would be better to not have known him. It is a serious and sacred experience.