Joseph Fielding Smith
“Question: ”Where did Alma get his authority? All we can find is that he received it from God, but there is no detail, and we are left to wonder if it was before he was baptized. We are confused about the whole matter and would appreciate any information you can give us."
"Answer: 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…Moreover, while the detail is lacking, the evidence is very clear that the Melchizedek Priesthood was possessed by the Nephites.
"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…
"The question is: 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.’" (Answers to Gospel Questions, vol. 4, pp. 161-164)