The irrevocable moral standard of the Lord and his Church is and has been forever the same: total and complete chastity before marriage and unconditional fidelity after marriage.
resident Joseph F. Smith said: “No more loathsome cancer disfigures the body and soul of society today than the frightful affliction of sexual sin. It vitiates the very fountains of life and bequeaths its foul effects to the yet unborn as a legacy of death.” (Cited in Gospel Ideals, p. 399.)
Likewise, President Spencer W. Kimball taught: “There is no compatibility between light and darkness. Unchastity is darkness. It is ugly, bitter, destructive, and consuming. It neutralizes good. It darkens minds. It produces spiritual amnesia. It comes in many ugly forms and has many distasteful names. It is born in the mind and is given expression with directed body members.
It is a tyrant, demanding and uncompromising and unreasonable, tending toward monopoly. It is like creeping paralysis, slipping up in the darkness, getting hold with its tentacles, and clings on so tenaciously that it takes a prince with a sharp sword to cut it loose.” (The Teachings of Spencer W Kimball, p. 271.)