God made them for eachother. It was a union created and overseen by God Himself rather than the appointed law which didn't exist at the time. Many laws and structures were set up later. God didn't state in the garden that they weren't to kill, steal, etc. because at that time man was without sin. He wouldn't have thought of touching someone God didn't give to him/her. But if you'll remember the tree of the knowledge of good and evil, the only law which they were commanded to obey, sin changed everything in the world. And God made the first blood sacrifice fo their sin in one of His animals to clothe the newly realized naked sinners. There are also practical reasons why it is a bad idea to have pre-marital sex, but since that isn't asked I'll leave it alone.

In Genesis 2:23-26, BEFORE the fall, God created man in His own image, male and female He created them and told them to "be fruitful and multiply". In Genesis 2:24&25, God said, "...a man will leave his father and mother and be united to his WIFE, and they will become one flesh. The man and his WIFE were both naked and they felt no shame. Marriage is an institution that God established and we as humans have really messed up. Marriage doesn't mean "'til death do us part" anymore. Now it means 'til it's inconvenient, 'til I find someone else, "'til I decide that I maybe I want to be free", etc. The Bible gives us rules to live by. If we follow the rules, we'll be OK, but if we decide that we know a better way then we will have to accept the consequences of our actions.

The essential requirements for marriage are: Eligible adult man and woman Mutual consent Promise to live together in lifelong faithfulness Public ceremony With God as the preacher, you have a ceremony with all the necessary elements recorded on the pages of Holy Scripture, which is about as public as you can get. So they were married.

It is widely believed that the apple from the Tree of the Knowledge of Good and Evil represents sex. I.e. the story of eating the apple is a euphemism for having sex. In which case, the reason that they got thrown out of Eden was precisely because they had premarital sex. Presumably God only invented the institution of marriage later to handle the problem if Adam and Eve's children, and their wives who seem to have appeared out of nowhere.

"And they were both naked, the man and his wife, and were not ashamed." Genesis 2:25 "And they heard the voice of the LORD God walking in the garden in the cool of the day: and Adam and his wife hid themselves from the presence of the LORD God amongst the trees of the garden." Genesis 3:8 There are more references in the Bible which show that they were indeed husband and wife. Christians are against pre-marital sex because one of the Ten Commandments is "Thou shalt not commit adultery." (Exodus 20: 14) Hope this helps.

They were married by God himself. God brought the woman Eve, to Adam. God spoke to them both in the garden of Eden. There would not have been exactly the same ceremony we see today. First of all, there were no witnesses. Only Adam and Eve and God.

In answer to your question "why are Christians against premarital sex": God made sex to be something beautiful, a source of joy and happiness. He also designed it to be within the commitment of a marriage. This is where it is at its best. And where it becomes a sign of unity and an expression of mutual commitment and love. Sex outside of marriage avoids commitment and intimacy, leaving us more lonely than ever - the kind of sex that can never "become one." God urges us to ":guard the sacredness of sexual intimacy between wife and husband." (Hebrews 13:4) He also wants to protect you psychologically and to protect your body from disease--because he loves you. He laid down the rules so that you could have the best of life, complete happiness and fulfillment. God's plans for you are for your welfare and peace, plans to take care of you and give you a hope and a future. (Jeremiah 29:11) After all, he loves you so much he gave his very life just to be with you. He died so that you could live--so that you could have an "abundant", fulfilled, "complete", "real", "full", love-filled, eternal life---a life far better than you could ever have on your own (verse). Let me quote Billy Graham, he says it well: "...We have to have rules to live by. And what we're saying is we're going to play a baseball game without any rules, we're going to play a football game without any rules, we're going to live a life without any moral rules. Well God has laid down certain rules and said "If you want the best of life, if you want complete happiness and fulfillment, live by these rules.' And one of those rules is that 'thou shalt not commit immorality.' "Most pychologists today and most psychiatrists I think would agree with the Bible, that there are very serious problems involved. God did not say 'thou shalt not commit immorality before marriage in order to keep you from having a good time or having fun.' He said that to protect you. To protect you psychologically, to protect your body, because today venereal disease is at an all time high dispite all of our problems and illigeitmacy is at an all time high inspite of all our medical science...And all of these things God has said 'I want to make you happy, I want to help you, and I've given you some rules to live by and this is the rules.' "...The Bible clearly teaches that all sexual relations outside marriage are wrong in God's eyes. The Bible bluntly says, "Flee from sexual immorality" (1 Corinthians 6:18). This includes any kind of sexual activity apart from marriage. "Remember that God gave us the gift of sex in the first place—and He intended for it to be a source of joy and happiness for us. But He also intended for it to be restricted to marriage. Why? One reason is because it was to be a sign of the unity between a husband and wife. It was, in other words, meant to be an expression of their mutual commitment and love. But sex outside marriage easily becomes selfish, and even boring. "God knows what is best for us, including this important area of our lives. Why ignore His way, when it is best for us in the long run? The Bible warns, 'There is a way that seems right to a man, but in the end it leads to death' (Proverbs 14:12) The Bible also promises, 'Blessed are they whose ways are blameless' (Psalm 119:1). "...With God's help we can follow a far better path." Hebrews 13:4: "Honor marriage, and guard the sacredness of sexual intimacy between wife and husband. God draws a firm line against casual and illicit sex." Jeremiah 29:11 (combining the MSG and Amplified): "For I know the thoughts and plans that I have for you, says the Lord, thoughts and plans for welfare and peace"/"to take care of you, not abandon you"/"not for evil"/"plans to give you the future you hope for."

They were married by God himself!