D&C 110

After several visions had been manifested to the Prophet Joseph Smith and Oliver Cowdery in the Kirtland Temple, the prophet records -

"...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:
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)

The keys of the priesthood that was restored by was the sealing power. The same power the Savior referred to while speaking to Peter -

"...I will give unto thee the keys of the kingdom of heaven: and whatsoever thou shalt bind on earth shall be bound in heaven: and whatsoever thou shalt loose on earth shall be loosed in heaven." (New Testament Matthew 16:19)

The keys of this sealing power that without such -

"...All covenants, contracts, bonds, obligations, oaths, vows, performances, connections, associations, or expectations...are of no efficacy, virtue, or force in and after the resurrection from the dead..." (Doctrine and Covenants Section 132:7)

These last keys restored by the prophet Elijah are the crowning keys to all other keys and were restored last as -

"Behold, mine house is a house of order, saith the Lord God..." (Doctrine and Covenants Section 132:8)

Last Thursday, I was able to witness the manifestation of this great sealing power at the wedding of my daughter. I can testify without any hesitation that the Spirit witnessed to me that this power has been restored and so demonstrated in the temple that day.

"Therefore, in the ordinances thereof, the power of godliness is manifest." (Doctrine and Covenants Section 84:20)