Another great and glorious vision burst upon us; for Elijah ... and said: Behold, the time has fully come, which was spoken of by the mouth of Malachi—testifying that he [Elijah] should be sent, before the great and dreadful day of the Lord. Doctrine & Covenants 110:13

Trivia: What river was especially cursed by God in Section 61 of the Doctrine and Covenants?