3 Nephi 25

As the Savior delivered to the Nephites, that which He had previously revealed to Malachi, He said -

"FOR behold, the day cometh that shall burn as an oven; and all the proud, yea, and all that do wickedly, shall be stubble; and the day that cometh shall burn them up, saith the Lord of Hosts, that it shall leave them neither root nor branch." (Book of Mormon 3 Nephi 25:1)

What did He mean that He would leave them neither root nor branch? I believe it had a great deal to do with the restoration of the priesthood and the sealing power. The Lord continued saying -

"Remember ye the law of Moses, my servant, which I commanded unto him in Horeb for all Israel, with the statutes and judgments." (Book of Mormon 3 Nephi 25:4)

As I read this verse, it seems more like a query. Like - if you remember this, there is something more of greater significance for -

"Behold, I will send you Elijah the prophet before the coming of the great and dreadful day of the Lord;
6 And he shall 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." (Book of Mormon 3 Nephi 25:5 - 6)

The curse being -

"...that it shall leave them neither root nor branch..." (Book of Mormon 3 Nephi 25:1)

Root or branch has to do with what we envision as a family tree. The root being our ancestors and the branch, our posterity. With out this special sealing power that binds in heaven what is bound (or sealed) on earth, families relationships would be lost in the eternities leaving man with neither root nor branch.

We recognize this sealing power of the priesthood with Nephi as the Lord said -

"Behold, I give unto you power, that whatsoever ye shall seal on earth shall be sealed in heaven; and whatsoever ye shall loose on earth shall be loosed in heaven; and thus shall ye have power among this people." (Book of Mormon Helaman 10:7)

It was this sealing power that in 1836, in the Kirtland Temple, a -

"...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)

Joseph Field Smith said -

"...This sealing power, restored in this dispensation by Elijah the Prophet (D. & C. 2:1-3; 110:13-16), is the means whereby "All covenants, contracts, bonds, obligations, oaths, vows, performances, connections, associations, or expectations" attain "efficacy, virtue, or force in and after the resurrection from the dead." (D. & C. 132:7.)

All things that are not sealed by this power have an end when men are dead. Unless a baptism has this enduring seal, it will not admit a person to the celestial kingdom; unless an eternal marriage covenant is sealed by this authority, it will not take the participating parties to an exaltation in the highest heaven within the celestial world.

All things gain enduring force and validity because of the sealing power. So comprehensive is this power that it embraces ordinances performed for the living and the dead, seals the children on earth up to their fathers who went before, and forms the enduring patriarchal chain that will exist eternally among exalted beings..." (Doctrines of Salvation, vol. 2, pp. 115-128.)