3 Ne.11:21; Answers to Gospel Questions, Smith, 3:205-206; 4:95-97
“When Christ appeared to the Nephites on this continent, he commanded them to be baptized, although they had been baptized previously for the remission of their sins… . We read that the Savior commanded Nephi and the people to be baptized again, because he had organized anew the Church under the gospel. Before that it had been organized under the law.” (Joseph Fielding Smith, Doctrines of Salvation 2:336)