"But greater than all this, so far as our individual responsibilities are concerned,
the greatest is to become saviors, in our lesser degree which is assigned us,
for the dead who have died without a knowledge of the Gospel. Joseph Smith said:
"The greatest responsibility in this world that God has laid upon us, is to seek
after our dead."…It will suffice here to say that the Lord has placed upon us
this responsibility of seeing our dead receive the blessings of the Gospel. Said
Joseph Smith: "Those saints who neglect it, in behalf of their deceased relatives,
do it at the peril of their own salvation."
Joseph Fielding Smith
The Way to Perfection p153-154