BYU Speeches of the Year, 1966, Elder Theodore M. Burton; “The greatest responsibility in this world that God has laid upon us is to seek after our dead. (Joseph Fielding Smith, Teachings of the Prophet Joseph Smith, p. 356.) The Prophet also said: This doctrine was the burden of the scriptures. Those saints who neglect it in behalf of their deceased relatives, do it at the peril of their own salvation. (Ibid., p. 193.)”
Luke 11:23: “He that is not with me is against me: and he that gathereth not with me scattereth.”
Jesus also told His disciples to let the dead bury their dead and to go out to preach the Kingdom of Heaven. You cannot save the dead.