The Seventh Commandment states that we are not to commit adultery (Exodus 20:14). When God made the first man Adam He saw that it was not good for him to be without a companion (1) (Genesis 2:18). However, no animal was worthy to be called the helpmate or wife of the man (Genesis 2:20). Therefore, God put the first man Adam to sleep and from his side took cells from which he made a woman, and Adam named her Eve (Genesis 2:21-23. Genesis 3:20). This is the pattern for the nuclear family on Earth - one male and one female united for life (Genesis 2:24). Not two males or two females (1) - again, the pattern was Adam and Eve, not Adam and Steve or Eve and Louise! Consequently, the phrase "same-sex marriage" is an oxymoron.
Within this male and female marriage relationship God provided and blessed sex (1) in order for the two to enjoy an incredibly pleasurable intimacy (i.e., "into-me-see") spirit, soul and body (1 Corinthians 7:3-5). This pleasurable union where the married male and female are joined as one can result in the physical joining of the male sperm and the female egg where literally the two become one NEW flesh - a baby! (Matthew 19:4-6. Ephesians 5:31. Genesis 4:1) God designed sex to take place between a married male and female with any deviation from this referred to as adultery. Adultery is sex with someone that we are not married to that is married to someone else or is not married. Sexual immorality (fornication) is sex before marriage, self-sex, same-gender sex (Leviticus 18:22), or sacrilegious sex (e.g., bestiality (Leviticus 18:23,24), anal, oral, incest (Leviticus 18:6), or violent sex, etc.), etc. Adultery destroys trust in and out of marriage - it is being unfaithful. It is rejection and betrayal of the cruelest type; consequently, God forbids it (Exodus 20:14).
The Law of Consequence for Violating the Commandment
The Bible is replete with warnings for those that chose to ignore God's command to only having sex within God's definition of marriage:
Proverbs 2:10-19. Proverbs 5:1-17. Proverbs 6:23-35. Proverbs 7:1-27. Proverbs 22:14. Proverbs 30:20. Proverbs 31:3. Ecclesiastes 7:26. Malachi 2:13-16. 1 Corinthians 6:9-11. 1 Corinthians 6:13-18. Galatians 5:19-21. Ephesians 5:5,6. Colossians 3:5,6. Hebrews 13:4. Jude 1:7. Revelation 21:8. Romans 1:26-29. Revelation 2:20-22.
Well, you say that you have never done those things? Have you ever fantasized (1) about having sex with someone perhaps while performing self-sex? Then you are still guilty (Matthew 5:27,28. Job 31:1). If You Can't Say "Amen", Say "Oh Me!" (1)
The Opportunity of Blessing for Keeping the Commandment
Those that choose to only have sex within the confines of God's definition of marriage will find that it is the oil of marriage that minimizes the friction in life. Just as in Commandments 10 (1), 9 (1) and 8 (1) to walk in love towards your spouse (1) will fulfill this law (Proverbs 5:18-23. 1 Corinthians 7:3-5. 1 Thessalonians 4:3-5).
(1) Left click on the underlined phrase to open another article in a different tab with more explanation.