Rod of Iron
For Christ also hath once suffered for sins, the just for the unjust, that he might bring us to God, being put to death in the flesh, but quickened by the Spirit: By which also he went and preached unto the spirits in prison; Which sometime were disobedient, when once the longsuffering of God waited in the days of Noah, while the ark was a preparing, wherein few, that is, eight souls were saved by water. The like figure whereunto even baptism doth also now save us (not the putting away of the filth of the flesh, but the answer of a good conscience toward God,) by the resurrection of Jesus Christ. (1 Peter 3:18-21)
Our beloved Apostle Paul also alludes to the fact that the Gospel is preached unto the dead, when he uses the doctrine of baptism for the dead (which the ancient Saints practiced) to prove the Resurrection. Said he, "Else what shall they do which are baptized for the dead, if the dead rise not at all? why are they then baptized for the dead? (1 Cor. 15:29)" The words of Nephi in concert with Peter and Paul's words, give extra proof to the validity of the doctrine of baptism for the dead.
I know that the Church of Jesus Christ of Latter-day Saints is true, and the only true and living Church upon the earth. I know that Jesus is the Christ, and that if we give heed to His words, we will be led aright. I know the Lord had provided the scriptures for us to learn of Him and His teachings. In the name of Jesus Christ, amen.