Summary: There are significant positive results that make sex a sacred and profound endeavor, one that deserves special treatment. There are also negative consequences associated with sexual promiscuity.
Ephesians 5:3 But among you there must not be even a hint of sexual immorality, or of any kind of impurity, or of greed, because these are improper for God’s holy people.
Let's Talk About Sex
Sex is good. The Bible has taught this, literally, from the beginning. God's first commandment to humanity was "Be fruitful and multiply, and fill the earth" (Genesis 1 & 9). This commandment came long before any of the Thou Shalt Not's.
A few observations about that commandment:
1. God didn't say 'have sex & multiply", He said "Be fruitful & multiply". You can understand it as "have lots of sex and make lots of babies". But it seems like there is something more here, like fruitfulness is essential-God doesn't say do something, He says be something. Be fruitful. Sex is fundamental to our being. The fruitfulness sex enables is beautiful.
2. Sex has results. It is pleasurable (remember Sarah, when she was about 90 years old, said "shall I have pleasure, even when I am old?" when God promised her a son in her old age). But sex is not pleasure merely for pleasure's sake.
Sex has at least two results for which it was created. First, it is the means by which the two become one. One man, and one woman become one flesh (Genesis 2), one + one = one. Sex is the means by which God brings two people together in a form of intimacy that is both profound and fulfilling. This alleviates the first thing in creation that was not good. At the end of God's creative work in Genesis 1, God said over and over, "it is good", literally, very good. The first thing that was not good was that man was alone, without a mate. Sex enables two people to become one physically, emotionally, mentally and spiritually (this is one reason the Bible teaches it should be engaged in with such exclusivity). Thereby it alleviates the loneliness of our natural state. Sex is not the only means of intimacy in a relationship, but it is an important part of it. Maybe this is part of the reason the ancient Hebrew word for having sex was to "know" (Adam knew his wife Eve and she conceived, Genesis 4:1). The sharing of sex is so complete it knits two souls together. The second result is life.
I think we talk too little about how profound a privilege God has given us of bringing life into the world. Through sex, a physical act, a human, a spiritual being, is brought into existence. Without our cooperation that eternal being would not have a chance at life. When i was a child, most people thought of having children as one of their greatest goals. These days many people think of children as an inconvenience-a hinderance to accomplishing their goals. Families encourage young people to finish their education and build a career before having children, as if those things are first, or primary. If one is thinking of education and career as means to raise children in a more secure environment, there may be some validity to the argument. But i think most people are not necessarily reasoning in that way. Bringing eternal living beings into existence and raising them well is a far greater accomplishment than any degree or career, or fame, or individual achievement will ever be.
So, there are significant positive results that make sex a sacred and profound endeavor, one that deserves special treatment. There are also negative consequences associated with sexual promiscuity.
I don't like scare tactics, and they are not effective in changing people's behavior. Having said that, there are horrible potential consequences to sexual promiscuity. The most obvious is sexually transmitted diseases, or STD's. There are many STD's that can lead to serious illness and death (five are listed and described here http://www.std-gov.org/blog/top-5-most-dangerous-stds/ ). All of them can be passed on through sexual intercourse, and most even through deep kissing. This is certainly one of the reasons the Bible discourages promiscuity. Before the last century treatments for these diseases didn't exist. God loves us enough to want to spare us these consequences. A couple that enters marriage as virgins, who lives a strictly monogamous life, has almost zero chance of contracting a STD. Obviously, medical procedures can reduce the horrors of most of these diseases today. That doesn't change the fact that the most natural way to prevent them is monogamous, heterosexual sex.
The other issue the Bible talks about concerning sex is the matter of the heart. Our heart is bound to the one with whom we have sexual relations. God warned the kings of Israel not to multiply wives, because those unions would turn their hearts away from God (Deuteronomy 17:17). The connections we make with a sexual partner are all-encompassing. When we engage in this sharing we change our hearts. Recent research indicates we also change the wiring of our brains. We are changed by sexual behavior in ways that we are only beginning to understand. It is an important part of our identity that we must learn to bring before the throne of our Lord, along with everything else, and submit to Him. Only in this way we can learn the righteousness of God.