The Fall of Adam and Eve

Doctrine and Covenants 29:40–41

40 Wherefore, it came to pass that the devil tempted Adam, and he partook of the forbidden fruit and transgressed the commandment, wherein he became subject to the will of the devil, because he yielded unto temptation.
41 Wherefore, I, the Lord God, caused that he should be cast out from the Garden of Eden, from my presence, because of his transgression, wherein he became spiritually dead, which is the first death, even that same death which is the last death, which is spiritual, which shall be pronounced upon the wicked when I shall say: Depart, ye cursed.

President Joseph Fielding Smith wrote:

“When Adam transgressed in the Garden of Eden he died the spiritual death, as well as changing his nature and bringing upon himself mortality. Spiritual death is banishment from the presence of God, and Adam was shut out from the presence of the Lord. Angels were sent to him, however, to teach him the plan of salvation. The earth probation was prolonged that he might repent and accept the plan offered to him. Through his repentance, baptism, and confirmation, he was brought back again into the presence of God through the Holy Ghost. This same spiritual death comes upon all unrepentant and unbaptized men, and the only way they can be brought from spiritual death to spiritual life is through obedience to the gospel. By this means all men may be redeemed, as Adam was, from the spiritual fall, but all who will not receive the gospel ‘cannot be redeemed from their spiritual fall, because they repent not’ [D&C 29:44]. The ‘second death’ is like the first death, spiritual banishment, but this death will be discussed hereafter.”

(Church History and Modern Revelation, 2 vols. [1953], 1:144.)