"All of this should be conveyed without having priesthood leaders focus upon intimate matters which are a part of husband and wife relationships. Skillful interviewing and counseling can occur without discussion of clinical details by placing firm responsibility on individual members of the Church to put their lives in order before exercising the privilege of entering a house of the Lord. The First Presidency has interpreted oral sex as constituting an unnatural, impure, or unholy practice. If a person is engaged in a practice which troubles him enough to ask about it, he should discontinue it."
- Official Declaration of the First Presidency of the Church, January 5th, 1982
"Prophets anciently and today condemn masturbation. It induces feelings of guilt and shame. It is detrimental to spirituality. It indicates slavery to the flesh, not that mastery of it and the growth toward godhood which is the object of our mortal life. Our modern prophet has indicated that no young man should be called on a mission who is not free from this practice. What is more, it too often leads to grievous sin, even to that sin against nature, homosexuality. For, done in private, it evolves often into mutual masturbation-practiced with another person of the same sex and thence into total homosexuality...."
- Prophet Spencer W. Kimball, The Miracle of Forgiveness, Pages 77-79, 81-82
"Among the most common sexual sins our young people commit are necking and petting. Not only do these improper relations often lead to fornication, [unwed] pregnancy, and abortions - all ugly sins - but in and of themselves they are pernicious evils, and it is often difficult for youth to distinguish where one ends and another begins. They awaken lust and stir evil thoughts and sex desires. They are but parts of the whole family of related sins and indiscretions. Almost like twins, 'petting' and fornication are alike."
- Prophet Spencer W. Kimball, The Miracle of Forgiveness, page 65
"Also far-reaching is the effect of the loss of chastity. Once given or taken or stolen it can never be regained. Even in a forced contact such as rape or incest, the injured one is greatly outraged. If she has not cooperated and contributed to the foul deed, she is of course in a more favorable position. There is no condemnation where there is no voluntary participation. It is better to die in defending one's virtue than to live having lost it without a struggle."
- Prophet Spencer W. Kimball, The Miracle of Forgiveness, page 196
"And Cain said unto the Lord, My punishment is greater than I can bear. Behold, thou hast driven me out this day from the face of the earth." (Genesis 4:9-14.) That was true of murder. It is also true of illicit sex, which, of course, includes all petting, fornication, adultery, homosexual acts, and all other perversions. The Lord may say to offenders, as He did to Cain, "What hast thou done?" The children thus conceived make damning charges against you; the companions who have been frustrated and violated condemn you; the body that has been defiled cries out against you; the spirit which has been dwarfed convicts you. You will have difficulty throughout the ages in totally forgiving yourself."
-Prophet Spencer W. Kimball, "Love Versus Lust", BYU Speech January 5, 1965. Often-used quote still used today in LDS seminary classes.
"I do not find in the Bible the modern terms "petting" nor "homosexuality," yet I found numerous scriptures which forbade such acts under by whatever names they might be called. I could not find the term "homosexuality," but I did find numerous places where the Lord condemned such a practice with such vigor that even the death penalty was assessed."
- Apostle Spencer W. Kimball, "Love Versus Lust", BYU Speech January 5, 1965
"If adultery or fornication justified the death penalty in the old days, and still in Christ's day, is the sin any less today because the laws of the land do not assess the death penalty for it? Is the act less grievous? There must be a washing, a purging, a changing of attitudes, a correcting of appraisals, a strengthening toward self-mastery. There must be many prayers, and volumes of tears. There must be an inner conviction giving to the sin its full diabolical weight. There must be increased devotion and much thought and study. And this takes energy and time and often is accompanied with sore embarrassment, heavy deprivations and deep trials, even if indeed one is not excommunicated from the Church, losing all spiritual blessings."
-Prophet Spencer W. Kimball, The Miracle of Forgiveness, Page 155
"How like the mistletoe is immorality. The killer plant starts with a sticky sweet berry. Little indiscretions are the berries -- indiscretions like sex thoughts sex discussions, passionate kissing, pornography. The leaves and little twigs are masturbation and necking and such, growing with every exercise. The full-grown plant is petting and sex looseness. It confounds, frustrates, and destroys like the parasite if it is not cut out and destroyed, for, in time it robs the tree, bleeds its life, and leaves it barren and dry; and, strangely enough, the parasite dies with its host."
- Apostle Spencer W. Kimball, General Conference Address, April 1, 1967.
https://exploringmormonism.com/boyd-k-packer-and-a-whole-new-sin/