The Prophet Jacob is one of the great theologians of the Atonement.
O how great the holiness of our God! For he knoweth all things, and there is not anything save he knows it. And he cometh into the world that he may save all men if they will hearken unto his voice; for behold, he suffereth the pains of all men, yea, the pains of every living creature, both men, women, and children, who belong to the family of Adam. And he suffereth this that the resurrection might pass upon all men, that all might stand before him at the great and judgment day. [2 Nephi 9:20–22]
For as death hath passed upon all men, to fulfil the merciful plan of the great Creator, there must needs be a power of resurrection, and the resurrection must needs come unto man by reason of the fall; and the fall came by reason of transgression; and because man became fallen they were cut off from the presence of the Lord. Wherefore, it must needs be an infinite atonement—save it should be an infinite atonement this corruption could not put on incorruption. Wherefore, the first judgment which came upon man must needs have remained to an endless duration. . . .
Now the first judgment which came upon man was “thou shalt surely die.” It involved both of those deaths, the death of the body and the death as to things pertaining to righteousness, which the scriptures call spiritual death.
O the wisdom of God, his mercy and grace! For behold, if the flesh should rise no more [that is, if there were no resurrection of the body] our spirits must become subject to that angel who fell from before the presence of the Eternal God, and became the devil, to rise no more. And our spirits must have become like unto him, and we become devils, angels to a devil, to be shut out from the presence of our God, and to remain with the father of lies, in misery, like unto himself. . . .
O how great the goodness of our God, who prepareth a way for our escape from the grasp of this awful monster; yea, that monster, death and hell, which I call the death of the body, and also the death of the spirit. [2 Nephi 9:6–10]