Alma’s Authority to Baptize

Church Educational System
We may conclude that Alma held the priesthood before he, with others, became disturbed with King Noah. Whether this is so or not makes no difference because in the Book of Mosiah it is stated definitely that he had authority.

‘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’ [ Mosiah 18:13].

If he had authority to baptize that is evidence that he had been baptized. Therefore, when Alma baptized himself with Helam that was not a case of Alma baptizing himself, but merely as a token to the Lord of his humility and full repentance.

(Joseph Fielding Smith, Answers to Gospel Questions, 3:203)

Book of Mormon Student Manual (1996 Edition)

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