Malachi closes his book with the statement by the Savior that “before the coming of the great and dreadful day of the Lord” Elijah should come to “turn the heart of the fathers to the children, and the heart of the children to their fathers, lest I come and smite the earth with a curse.” (3 Nephi 25:5-6. See also Malachi 4:5-6; Joseph Smith 2:37-39.
Many biblical scholars have assumed that the prophesied “second coming of Elijah” took place during the lifetime of the Savior when Elijah appeared on the Mount of Transfiguration. (See Mark 9:4.) However, the fact that the Savior quoted this prophecy to the Nephites after his resurrection would indicate the fulfillment was still in the future. Also, a careful wording of this scripture indicates that the prophesied coming of Elijah pertained not to the first coming of the Savior, but to his second coming; Malachi said that Elijah the prophet should be sent before the coming of “the great and dreadful day of the Lord.” The first coming of the Savior was a great day, but it was not dreadful; however, the second coming of the Savior will be both a great day (for the righteous) and a dreadful day (for the wicked).
Final proof that this prophecy pertains to the last days is found in the statement by Joseph Smith that on September 21, 1823, the angel Moroni quoted this prophecy and said it was about to be fulfilled. (See Joseph Smith 2:36-40.) Most Latter-day Saints believe this prophecy was fulfilled on April 3, 1836, when Elijah appeared in the Kirtland Temple and restored the sealing powers of the priesthood. The Doctrine and Covenants records the following concerning this visitation:
… another great and glorious vision burst upon us; for Elijah the prophet, who was taken to heaven without tasting death, stood before us, 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 come—
To turn the hearts of the fathers to the children, and the children to the fathers, lest the whole earth be smitten with a curse—
Therefore, the keys of this dispensation are committed into your hands; and by this ye may know that the great and dreadful day of the Lord is near, even at the doors. (D&C 110:13-16.)