While the world was in darkness—metaphorically in Jerusalem and literally in the New World—gospel light was shining where it had not shone so brightly before. Although the Book of Mormon clearly teaches that the redemptive power of the Atonement allowed believers long before Jesus’ mortal ministry to have faith in Christ and repent of their sins, one aspect of his saving work could not be realized until his own death and resurrection. For even the righteous dead “looked upon the long absence of their spirits from their bodies as a bondage” (D&C 138:50).
... The expression “spirits in prison” (1 Peter 3:19) led to the Latter-day Saint concept of a postmortal “spirit prison” where those who did not know the gospel of Jesus Christ remained until they were taught and accepted it. But it was not until 1918 when President Joseph F. Smith received the vision of the redemption of the dead that the relationship between Jesus Christ and those in spirit prison—the righteous dead on the one hand and the disobedient or untaught dead on the other—was understood. Of his revelation, President Smith explained that as he pondered the words of Peter, a vision opened up to him of the hosts of the dead. His attention was particularly drawn to the “spirits of the just, who had been faithful in the testimony of Jesus while they lived in mortality” (D&C 138:12). Among these were Father Adam, glorious Mother Eve, and a great assembly of ancient prophets. Though righteous, they, like all the dead, considered the separation of their spirits from their bodies as a type of captivity (D&C 138:50).
President Smith saw that it was this group, the faithful and believing dead, that the spirit of Jesus visited while his body lay in the tomb: “While this vast multitude waited and conversed, rejoicing in the hour of their deliverance from the chains of death, the Son of God appeared, declaring liberty to the captives who had been faithful; and there he preached to them the everlasting gospel, the doctrine of the resurrection and the redemption of mankind from the fall, and from individual sins on conditions of repentance” (D&C 138:18–19). The response, according to President Smith, was that “the saints rejoiced in their redemption, and bowed the knee and acknowledged the Son of God as their Redeemer and Deliverer from death and the chains of hell” (D&C 138:23).
The revelation explains that Jesus did not go personally among the wicked or the rebellious spirits. Rather, from among the righteous dead he organized a great missionary force to preach the gospel “to those who had died in their sins, without a knowledge of the truth, or in transgression, having rejected the prophets. These were taught faith in God, repentance from sin, vicarious baptism for the remission of sins, the gift of the Holy Ghost by the laying on of hands, and all other principles of the gospel that were necessary for them to know in order to qualify themselves that they might be judged according to men in the flesh, but live according to God in the spirit. And so it was made known among the dead, both small and great, the unrighteous as well as the faithful, that redemption had been wrought through the sacrifice of the Son of God upon the cross” (D&C 138:32–35; emphasis added).
... The mission of Jesus to the spirit world—personally to the righteous and, by extension through their preaching, to the unrighteous—makes it possible that all of God’s children, regardless of knowledge or opportunities in this life, will be able to avail themselves of the great sacrifice of Jesus Christ. Indeed, Jesus’ mission to the spirit world is at the very heart of Latter-day Saints’ “building of the temples and the performance of ordinances therein for the redemption of the dead” (D&C 138:54). As I participate in researching or recording family history or officiating in the sacred ordinances of the house of the Lord, I think of my Savior between his death and resurrection, himself in the spirit world on that day, making it possible for all to come unto him and be saved. Indeed, being in the temple on Good Friday or the Saturday before Easter is, for me, an essential part of preparing myself for Easter.