And now, my dearly beloved brethren and sisters, let me assure you that these are principles in relation to the dead and the living that cannot be lightly passed over, as pertaining to our salvation. For their salvation is necessary and essential to our salvation, as Paul says concerning the fathers—that they without us cannot be made perfect—neither can we without our dead be made perfect. . . .
I might have rendered a plainer translation to this, but it is sufficiently plain to suit my purpose as it stands. It is sufficient to know, in this case, that the earth will be smitten with a curse unless there is a welding link of some kind or other between the fathers and the children, upon some subject or other—and behold what is that subject? It is the baptism for the dead. 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 128:15, 18).
Joseph Smith
What kind of characters are those who can be saved although their bodies are decaying in the grave? When his [God’s] commandments teach us, it is in view of eternity. The greatest responsibility in this world that God has laid upon us, is to seek after our dead.—The apostle [Paul] says, they without us cannot be made perfect. Now I will speak of them:—I say to you Paul, you cannot be perfect without us: it is necessary that those who are gone before, and those who come after us should have salvation in common with us, and thus hath God made it obligatory to man (April 1844 General Conference, Times and Seasons, 5:616).
Joseph F. Smith
The same principles that apply to the living apply also to the dead. … And so we are baptized for those that are dead. The living cannot be made perfect without the dead, nor the dead be made perfect without the living. There has got to be a welding together and a joining together of parents and children and children and parents until the whole chain of God’s family shall be welded together into one chain, and they shall all become the family of God and His Christ (Teachings of Presidents of the Church: Joseph F. Smith, Chapter 46: Redeeming Our Dead through Temple Service).
Russell M. Nelson
Any discussion of family responsibilities to prepare for exaltation would be incomplete if we included only mother, father, and children. What about grandparents and other ancestors? The Lord has revealed that we cannot become perfect without them; neither can they without us be made perfect. Sealing ordinances are essential to exaltation. A wife needs to be sealed to her husband; children need to be sealed to their parents; and we all need to be connected with our ancestors. . . .
In God’s eternal plan, salvation is an individual matter; exaltation is a family matter (October 2008 General Conference).