From "For the Strength of Youth", a publication written for the youth of the Church:
“The sacred powers of procreation are to be employed only between man and woman, lawfully wedded as husband and wife” (“The Family: A Proclamation to the World”).
Physical intimacy between husband and wife is beautiful and sacred. It is ordained of God for the creation of children and for the expression of love between husband and wife. God has commanded that sexual intimacy be reserved for marriage.
When you obey God’s commandment to be sexually pure, you prepare yourself to make and keep sacred covenants in the temple. You prepare yourself to build a strong marriage and to bring children into the world as part of a loving family. You protect yourself from the emotional damage that always comes from sharing physical intimacies with someone outside of marriage.
Do not have any sexual relations before marriage, and be completely faithful to your spouse after marriage. Satan may tempt you to rationalize that sexual intimacy before marriage is acceptable when two people are in love. That is not true. In God’s sight, sexual sins are extremely serious because they defile the power God has given us to create life. The prophet Alma taught that sexual sins are more serious than any other sins except murder or denying the Holy Ghost (see Alma 39:5).
Before marriage, do not do anything to arouse the powerful emotions that must be expressed only in marriage. Do not participate in passionate kissing, lie on top of another person, or touch the private, sacred parts of another person’s body, with or without clothing. Do not allow anyone to do that with you. Do not arouse those emotions in your own body.
In cultures where dating or courting is acceptable, always treat your date with respect, never as an object to be used for your lustful desires. Stay in areas of safety where you can easily control your physical feelings. Do not participate in talk or activities that arouse sexual feelings.
Homosexual activity is a serious sin. If you find yourself struggling with same-gender attraction, seek counsel from your parents and bishop. They will help you.
Victims of rape, incest, or other sexual abuse are not guilty of sin. If you have been a victim of any of these crimes, know that you are innocent and that God loves you. Seek your bishop’s counsel immediately so he can help guide you through the process of emotional healing.
If you are tempted to commit sexual transgressions, seek help from your parents, your bishop, and friends you can trust. Pray to the Lord, who will help you resist temptation and overcome inappropriate thoughts and feelings.
If you have committed sexual transgressions, begin the process of repentance now so you can find inner peace and have the full companionship of the Spirit. Seek the Lord’s forgiveness. Talk with your bishop. He will help you obtain the forgiveness available to those who truly repent.