Alma 12:16; Hel. 14:16; refer in this text to Alma 40:26; Doctrines of Salvation, Smith, 2:222
“One definition of the word spiritual is ‘of or pertaining to the spirit or things of the spirit’; the definition of death includes the idea of separation. Thus spiritual death rightfully refers to a state of spiritual separation from God; it may or may not have anything to do with a physical separation from God.” (Daniel H. Ludlow, Companion to Your Study of the Book of Mormon, p. 136)
“… all the world today, I am sorry to say, with the exception of a handful of people who have obeyed the new and everlasting covenant, are suffering this spiritual death. They are cast out from the presence of God. They are without God, without Gospel truth, and without the power of redemption; for they know not God nor His Gospel. In order that they may be redeemed and saved from the spiritual death which has spread over the world like a pall, they must repent of their sins, and be baptized by one having authority, for the remission of their sins, that they may be born of God. That is why we want these young men to go out into the world to preach the Gospel. While they themselves understand but little perhaps, the germ of life is in them.” (Joseph F. Smith, Conference Report, Oct. 1899, p. 72)