Question: Where did Alma the Elder get the legitimate priesthood authority to baptize at the waters of Mormon?

There were none of the tribe of Levi among them, therefore it was by virtue of the Melchizedek Priesthood that they officiated

In Mosiah, Alma the Elder teaches the words of Abinadi, and assembles a small group of believers, whom he baptizes:

And now it came to pass that Alma took Helam, he being one of the first, and went and stood forth in the water, and cried, saying: O Lord, pour out thy Spirit upon thy servant, that he may do this work with holiness of heart. And when he had said these words, the Spirit of the Lord was upon him, and he said: Helam, I baptize thee, having authority from the Almighty God, as a testimony that ye have entered into a covenant to serve him until you are dead as to the mortal body; and may the Spirit of the Lord be poured out upon you; and may he grant unto you eternal life, through the redemption of Christ, whom he has prepared from the foundation of the world. And after Alma had said these words, both Alma and Helam were buried in the water; and they arose and came forth out of the water rejoicing, being filled with the Spirit. And again, Alma took another, and went forth a second time into the water, and baptized him according to the first, only he did not bury himself again in the water (Mosiah 18꞉12–15).

Since Alma had been a wicked priest of King Noah, where did he receive the legitimate priesthood authority to baptize?

President Joseph Fielding Smith wrote:

We should take into consideration in the study of the Book of Mormon the fact that it is an abridgment taken from the records or history that had been kept by the prophets among the Nephites. Therefore, many of the details are lacking. This is equally true of the history of Israel as it has come down through the years to us in the Bible. We are left to accept the fact that Lehi, when he left Jerusalem, held divine authority and that this divine power was handed down from generation to generation until the time of the visitation of the Savior. Moreover, while the detail is lacking, the evidence is very clear that the Melchizedek Priesthood was possessed by the Nephites.

There were none of the tribe of Levi among them, therefore it was by virtue of the Melchizedek Priesthood that they officiated. There are many passages in the Book of Mormon in which reference is given to the Holy Priesthood. We should also remember that the record that we have received is an abridgment, and therefore many of the details are of necessity missing. Moreover, we are informed that many important things have been withheld from us because of the hardness of our hearts and our unwillingness, as members of the Church, to abide in the covenants or seek for divine knowledge.

In the case of Alma and his priesthood, we are left to surmise that he legally and divinely received it before the days of King Noah. We read that Zeniff, the father of Noah, was a righteous man. Alma evidently received the priesthood in the days of Zeniff, and at no time did he fully accept the teachings nor with full purpose follow the counsels and procedure of Noah and his wicked priests…

Just at what time Alma received the priesthood is not clearly stated, but we may presume that it occurred before Noah came to the throne. Moreover, we must also conclude that Alma at no time truly entered into the wickedness of this wicked king…

Where did Alma get his authority? Evidently he obtained it when he received the priesthood, which through his repentance he had not lost. There can be no serious question in relation to his authority, for it is written – “And it came to pass that Alma; having authority from God, ordained priests; even one priest to every fifty of their number did he ordain to preach unto them, and to teach them concerning the things pertaining to the kingdom of God” (Mosiah 18꞉18).^[1]

Latter-day Saint scholar and apologist Daniel C. Peterson wrote in a similar vein:

The case of Alma brings up at least two interesting questions: (1) Were the priests of Noah legitimate holders of legitimate priesthood, and (2) Where did Alma get his authority? We have to assume Alma and his one-time colleagues were ordained validly by Noah (Mosiah 11꞉5), who was also ordained validly by his father, Zeniff. The fact that Noah was not righteous after he was ordained and that Alma himself was part of Noah’s priestly group during his early ministry has nothing to do with Alma’s priesthood authority. Until superior priesthood authority withdraws permission to exercise priestly functions, a legitimately ordained holder of the priesthood continues to hold valid priesthood—however unrighteous he may be, however dead to spiritual promptings, and however unlikely it may be that he will ever actually exercise his priesthood.^[2]

Alma, in fact, claimed to have authority from God (Mosiah 18꞉13), a claim which Mormon implicitly acknowledges as valid (Mosiah 18꞉18). Alma was a descendant of Nephi (Mosiah 17꞉2), a fact which may or may not be significant in discussing his priesthood authority since we do not know precisely how the priesthood functioned or was apportioned among the Nephites. Certainly most, if not in fact all, of the priests and kings of whom we know anything in the Book of Mormon up to this point were of the lineage of Nephi. Furthermore, in the power vacuum left by the absence of king Noah, the people implored Alma to assume the royal title and prerogatives (Mosiah 23꞉6). He turned down the title, but out of necessity, he did carry out some kingly duties. Alma ordained priests and teachers for his outcast people, among whom he was in fact the sole human source of authority (Mosiah 18꞉18; 23꞉17).^[3]

We may begin to deal with one related but tangential question here: How is it that Alma retained his right to the priesthood if he was wicked? Doctrine and Covenants 121:35–37 states:

35 Because their hearts are set so much upon the things of this world, and aspire to the honors of men, that they do not learn this one lesson—

36 That the rights of the priesthood are inseparably connected with the powers of heaven, and that the powers of heaven cannot be controlled nor handled only upon the principles of righteousness.

37 That they may be conferred upon us, it is true; but when we undertake to cover our sins, or to gratify our pride, our vain ambition, or to exercise control or dominion or compulsion upon the souls of the children of men, in any degree of unrighteousness, behold, the heavens withdraw themselves; the Spirit of the Lord is grieved; and when it is withdrawn, Amen to the priesthood or the authority of that man.

This scriptures states that the power of the priesthood is withdrawn if the priesthood is used for unrighteous ends. How did Alma retain his priesthood? How did Noah validly ordain Alma? With regard to Noah we must, as Peterson states, assume that Noah at one time was validly ordained and that he subsequently validly ordained Alma. Notice the first sentence of verse 37: "That they may be conferred upon us, it is true;" Perhaps we can assume that the rights to receive the power of the priesthood can be conferred upon anyone at anytime. But the actual power and efficacy of the priesthood cannot be manifested unless we are righteous enough (in desires and/or works) to have that power manifested. Thus, for Alma to have the priesthood, the answer may lie in the fact that Alma repented of his sins. He followed Abinadi's exhortations and sought to follow God. God must have forgiven him of his sins as he repented so that he could organize the church and baptize people into it with true priesthood power.

Notes

1. ↑ Joseph Fielding Smith, Answers to Gospel Questions, 5 vols., (Salt Lake City, Utah: Deseret Book, 1957–1966), 4:161–162. ISBN 1573454400. GospeLink
2. ↑ Peterson inserts a footnote here, writing: The ancient Christian church faced this problem in the form of the Donatist schism, which was finally declared heretical in AD 405. The Donatists held that unrighteousness in a bishop or priest invalidated any and all ordinances that he might have performed. However, the Synod of Aries determined in AD 314. that the validity of baptisms and ordinations and the like did not depend upon the worthiness or merit of the officiator. (On the Donatists, and the related Novatianist and Meletian movements, see Christie-Murray 96–97.) Granted, the Christian church at this period was essentially apostate, but Latter-day Saints take basically the same position, and for good reason. If serious sin, as such, invalidated priesthood ordinances, we could never know whose marriage was legal, or who was really a member of the Church. Did the man who ordained you to the priesthood have a secret, unrepented sin? If he did, your ordination is invalid. Your mission was illegitimate, any converts you baptized are actually non-members, and you are living in adultery since you should never have been admitted to the temple. Any of your converts who served missions and baptized are similarly fraudulent, and the consequences ripple onward and outward in utterly unforeseeable ways. How could we ever be sure of anything?"
3. ↑ Daniel C. Peterson, "Priesthood in Mosiah," in The Book of Mormon: Mosiah, Salvation Only Through Christ, edited by Monte S. Nyman and Charles D. Tate, Jr. (Provo: Religious Studies Center, Brigham Young University, 1991), 187–210.