Elijah was an Old Testament prophet through whom mighty miracles were performed. He sealed the heavens, and no rain fell in ancient Israel for 3½ years. He multiplied a widow’s meal and oil. He raised a young boy from the dead, and he called down fire from heaven in a challenge to the prophets of Baal. (See 1 Kings 17–18.) At the conclusion of Elijah’s mortal ministry, he “went up by a whirlwind into heaven” (2 Kings 2:11) and was translated.
“We learn from latter-day revelation that Elijah held the sealing power of the Melchizedek Priesthood and was the last prophet to do so before the time of Jesus Christ” (Bible Dictionary, “Elijah”). The Prophet Joseph Smith explained, “The spirit, power, and calling of Elijah is, that ye have power to hold the key of the . . . fullness of the Melchizedek Priesthood . . . ; and to . . . obtain . . . all the ordinances belonging to the kingdom of God” (Teachings of Presidents of the Church: Joseph Smith , 311; emphasis added). This sacred sealing authority is essential for priesthood ordinances to be valid and binding both on earth and in heaven.
Elijah appeared with Moses on the Mount of Transfiguration (see Matthew 17:3) and conferred this authority upon Peter, James, and John. Elijah appeared again with Moses and others on April 3, 1836, in the Kirtland Temple and conferred the same keys upon Joseph Smith and Oliver Cowdery.
Scripture records that Elijah the prophet stood before Joseph and Oliver 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 110:14–16).
The restoration of the sealing authority by Elijah in 1836 was necessary to prepare the world for the Savior’s Second Coming and initiated a greatly increased and worldwide interest in family history research. — Elder David A. Bednar, “The Hearts of the Children Shall Turn,” Ensign, November 2011, pp. 25-26