The punishment for the sin of lust is expressly given, they shall not have the Spirit, but shall deny the faith and shall fear…and if he repents not he shall be cast out (DC 63:16, DC 42:23).
Gordon B. Hinckley
"The girl you marry can expect you to come to the marriage altar absolutely clean. She can expect you to be a young man of virtue in thought and word and deed. I plead with you boys tonight to keep yourselves free from the stains of the world…You must not fool around with the Internet to find pornographic material…You must not rent videos with pornography of any kind…Stay away from pornography as you would avoid a serious disease. It is as destructive. It can become habitual, and those who indulge in it get so they cannot leave it alone. It is addictive…it seduces and destroys its victims…I plead with you young men not to get involved in its use. You simply cannot afford to. The girl you marry is worthy of a husband whose life has not been tainted by this ugly and corrosive material." (Ensign, May 1998, p. 49 as taken from Latter-day Commentary on the Book of Mormon compiled by K. Douglas Bassett, p. 337)
Spencer W. Kimball
"Each person must keep himself clean and free from lusts…He must shun ugly, polluted thoughts and acts as he would an enemy. Pornographic and erotic stories and pictures are worse than polluted food. Shun them. The body has power to rid itself of sickening food. The person who entertains filthy stories or pornographic pictures and literature records them in his marvelous human computer, the brain, which can't forget such filth. Once recorded, it will always remain there, subject to recall." (Ensign, July 1978, pp. 3-7 as taken from Latter-day Commentary on the Book of Mormon compiled by K. Douglas Bassett, p. 335)
Howard W. Hunter
"A man who holds the priesthood shows perfect moral fidelity to his wife and gives her no reason to doubt his faithfulness. A husband is to love his wife with all his heart and cleave unto her and none else (see D&C 42:22-26). President Spencer W. Kimball explained:
"The words none else eliminate everyone and everything. The spouse then becomes pre-eminent in the life of the husband or wife and neither social life nor occupational life nor political life nor any other interest nor person nor thing shall ever take precedence over the companion spouse" (The Miracle of Forgiveness, Salt Lake City: Bookcraft, 1969, p. 250).
"The Lord forbids and his church condemns any and every intimate relationship outside of marriage. Infidelity on the part of a man breaks the heart of his wife and loses her confidence and the confidence of his children (see Jacob 2:35).
"Be faithful in your marriage covenants in thought, word, and deed. Pornography, flirtations, and unwholesome fantasies erode one's character and strike at the foundation of a happy marriage. Unity and trust within a marriage are thereby destroyed. One who does not control his thoughts and thus commits adultery in his heart, if he does not repent, shall not have the Spirit, but shall deny the faith and shall fear." (Conference Report, Oct. 1994)