[And after they had been received unto baptism, and were wrought upon and cleansed by the power of the Holy Ghost]: There are two parts to the Nephite baptism. The first is the rite of baptism, and the second is the receipt of the Holy Ghost:
“Joseph Smith explained that “baptism is a sign to God, to angels, and to heaven that we do the will of God, and there is no other way beneath the heavens whereby God hath ordained for man to come to Him to be saved, and enter into the Kingdom of God, except faith in Jesus Christ, repentance, and baptism for the remission of sins, and any other course is in vain; then you have the promise of the gift of the Holy Ghost” (Teachings of the Prophet Joseph Smith, 198). We often speak of being baptized to wash away our sins. That symbolism is helpful, and there is something to be gained from understanding water baptism as a cleansing. But the more powerful symbol is baptism as the death and burial of the old man of sin and the rise to newness of life (Romans 6:3-5).
The truth is, our sins are not really remitted in the baptism of water. In setting forth the doctrine of Christ, Nephi called upon his readers to “do the things which I have told you I have seen that your Lord and your Redeemer should do; for, for this cause have they been shown unto me, that ye might know the gate by which ye should enter. For the gate by which ye should enter is repentance and baptism by water; and then cometh a remission of your sins by fire and by the Holy Ghost” (2 Nephi 31:17; emphasis added). Truly, after people are received unto baptism, they are “wrought upon and cleansed by the power of the Holy Ghost” (Moroni 6:4).
The Holy Ghost is a sanctifier. After baptism we are “sanctified by the reception of the Holy Ghost” (3 Nephi 27:20). If we were to be immersed in water and then never be confirmed a member of the Church and receive the gift of the Holy Ghost, we would still be in our sins. “You might as well baptize a bag of sand as a man,” Joseph Smith pointed out, “if not done in view of the remission of sins and getting of the Holy Ghost. Baptism by water is but half a baptism, and is good for nothing without the other half—that is, the baptism of the Holy Ghost” (Teachings of the Prophet Joseph Smith, 314; see also 360).” (Robert L. Millet, Alive in Christ: The Miracle of Spiritual Rebirth [Salt Lake City: Deseret Book Co., 1997], 102.)
This dual aspect of baptism is also a feature of the many of the known descriptions of the early Christian baptismal practice in the Old World. The rite of immersion in water is accompanied with an anointing with the Holy Ghost. The two pieces might be differently ordered, with one preceding the other, or in one case, the anointing with the Holy Ghost occurring as the candidate was under water, but the connection between the two parts of a Christian baptism are quite clear in the ancient records. (Paul F. Bradshaw. The Search for the Origins of Christian Worship. Oxford University Press, 2002, pp. 144-170).
[they were numbered among the people of the church of Christ; and their names were taken]: The taking of the names is reminiscent of the covenant made by the people of Benjamin:
Mosiah 6:1
1 And now, king Benjamin thought it was expedient, after having finished speaking to the people, that he should take the names of all those who had entered into a covenant with God to keep his commandments.
The purpose of taking the names is not simply to have an official roll of the church, but to make explicit the covenant of the name. Each person has taken the name of Christ, and Christ has taken their name. There is an exchange of covenants and promises. Those who accept Christ have entered into a new relationship, and the taking of the names is symbolic of the receipt of that covenant.
[that they might be remembered]: The human aspect of taking the names allows the human officiators of God’s church to care for those who have made the commitments to the church. Without the names, there is no known community. In a sense, the ancient Christian was adopted into a new family. Christ was the new father, and they were sons and daughters of this new father:
Mosiah 5:7
7 And now, because of the covenant which ye have made ye shall be called the children of Christ, his sons, and his daughters; for behold, this day he hath spiritually begotten you; for ye say that your hearts are changed through faith on his name; therefore, ye are born of him and have become his sons and his daughters.
It is interesting that it is this rebirth symbolism that dominated some ancient commentaries on baptism, rather than the Pauline death/resurrection symbolism:
“A man comes out of that water reborn as a “son” of God… So it was that, in allusion to the concept of rebirth, some ancient commentators referred to the font as a womb, but never as a graved, and the idea of Romans 6:3-5 (of Christians being baptized into the death and resurrection of Christ) made no mark upon early Syrian thought about baptism.” (Paul F. Bradshaw. The Search for the Origins of Christian Worship. Oxford University Press, 2002, p. 149).
The Book of Mormon would follow this rebirth symbolism. The death/resurrection symbolism does not appear to play in the Nephite symbolic associations, and that would be consonant with the absence of the overt cross/death theology that was so important to the Old World that had to deal with a dying Savior, rather than the transcendent Atoning Messiah who appeared to the Nephites.
[and nourished by the good word of God, to keep them in the right way]: The baptism into the church was an adoption into a new family of God. In the ancient world, families had responsibilities to each other. Those who were of the same kin-group were expected to care for others of their kin. In this way, when one became “adopted” into the new “kin” of the church, there were social responsibilities owed by that new fictive kin-community to the newly baptized member. Their new brothers and sisters were to continue to teach them, and they were to encourage them to “keep… in the right way.”
These responsibilities of the community of faith continue in the latter day. The Lord has specifically directed us to teach our brethren:
Doctrine and Covenants 88:77
77 And I give unto you a commandment that you shall teach one another the doctrine of the kingdom. (italics added).
Similarly, the modern member of the church is also to care for our brethren, and see that we walk in the ways of the Lord:
Doctrine and Covenants 20:42
42 And to teach, expound, exhort, baptize, and watch over the church; (italics added)
[to keep them continually watchful unto prayer,]: One of the evidences of our continued relationship to God is prayer. If we continue in humility, we will continue to approach God in prayer, something that can only truly be done in humility. Once we attempt to pray without humility, our prayers are not longer directed to God (regardless of what we say in the prayer) but are rather directed to our vanity or our pride before men.
[relying alone upon the merits of Christ]: Christ is the only one capable of providing for our salvation:
Acts 4:12
12 Neither is there salvation in any other: for there is none other name under heaven given among men, whereby we must be saved.
[who was the author and the finisher of their faith.]: This phrase might be difficult to understand if we read “finisher” with the meaning of one who “ends” something. Of course Christ does not end our faith. However, a finisher is also one who completes something, and it is in that context that we can more readily understand this phrase. Christ is the author and the concluder. In other words, the analog of Alpha and Omega – the beginning and the end.