"He said there was a book deposited, written upon gold plates... He also said that the fulness of the everlasting Gospel was contained in it" (Joseph Smith—History 1:34).
This messenger [Moroni] proclaimed himself to be an angel of God, sent to bring the joyful tidings that... the Gospel in all its fullness to be preached in power, unto all nations that a people might be prepared for the Millennial reign. (History of the Church, 4:536–37)
Jesus Christ said of Joseph Smith: "And I will give unto him a commandment that he shall do none other work, save the work which I shall command him" (2 Nephi 3:8).
"Behold, I am Jesus Christ, whom the prophets testified shall come into the world" (3 Nephi 11:10).