D&C 2

One of the most important events to the eternal destiny and exaltation of man was foretold by Malachi, Moroni, and spoken by the Savior himself in ancient America was -

"BEHOLD, I will reveal unto you the Priesthood, by the hand of Elijah the prophet, before the coming of the great and dreadful day of the Lord.
2 And he shall plant in the hearts of the children the promises made to the fathers, and the hearts of the children shall turn to their fathers.
3 If it were not so, the whole earth would be utterly wasted at his coming." (Doctrine and Covenants Section 2:1 - 3)

Much of the world has little understanding of this prophecy. Elijah was to return with special keys of the priesthood that would give power to bind on earth and in heaven. A sealing power that ratifies or binds all ordinances done on earth in heaven. The Lord revealed that -

"...he that receiveth a fulness thereof must and shall abide the law, or he shall be damned, saith the Lord God.
7 And verily I say unto you, that the conditions of this law are these: All covenants, contracts, bonds, obligations, oaths, vows, performances, connections, associations, or expectations, that are not made and entered into and sealed by the Holy Spirit of promise, of him who is anointed... to hold this power in the last days...are of no efficacy, virtue, or force ...when men are dead." (Doctrine and Covenants Section 132:6 - 7)

Without this sealing power is it any wonder that -

"If it were not so, the whole earth would be utterly wasted at his coming." (Doctrine and Covenants Section 2:3)

President Joseph Fielding Smith wrote -

In other words, Elijah came to restore to the earth, by conferring on mortal prophets duly commissioned of the Lord, the fulness of the power of priesthood. This priesthood holds the keys of binding and sealing on earth and in heaven of all the ordinances and principles pertaining to the salvation of man, that they may thus become valid in the celestial kingdom of God.” (Doctrines ofSalvation, 2:111–12, 117.)

But not only does this sealing power ratify all ordinance and covenants but binds families together in the eternities. The Lord revealed regarding the promises made to the fathers -

"...For we without them cannot be made perfect; neither can they without us be made perfect. Neither can they nor we be made perfect without those who have died in the gospel also; for it is necessary in the ushering in of the dispensation of the fulness of times, which dispensation is now beginning to usher in, that a whole and complete and perfect union, and welding together of dispensations, and keys, and powers, and glories should take place, and be revealed from the days of Adam even to the present time. And not only this, but those things which never have been revealed from the foundation of the world, but have been kept hid from the wise and prudent, shall be revealed unto babes and sucklings in this, the dispensation of the fulness of times." (Doctrine and Covenants Section 128:18)

It is important to know that the prophecied coming of Elijah was fulfilled on April 3, 1836 in the Kirtland Temple as Joseph Smith testified -

"...for Elijah the prophet, who was taken to heaven without tasting death, stood before us, and said:
14 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—
15 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—
16 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." (Doctrine and Covenants Section 110:13 - 16)

Is it any wonder that in the coming of our Lord Jesus Christ that it will be a "great" day for some and a "dreadful" day for many others.