It simply means that sex is from God–he created it–and that it is given to us by him for our good and enjoyment. As the creator of sex, we can expect God to know best how it is to be expressed and enjoyed. If he places boundaries around its expression (and he does) we can reasonably assume those boundaries are established for our good. Why? Because he created us, too–and because he loves us.
In most other areas, we do not easily dismiss the instructions that come with good gifts. If we want to make the most of our gift, we will be sure to follow them carefully. For example, if, on your 16th birthday, you are gifted with a car, your car will come with an owner’s manual. That manual will contain lots of information that will affect the performance of the car: tire pressure, gas quality, oil change frequency, battery life, etc. Your car might also come with loving (but seemingly restrictive) instructions from the parents who gave it. Instructions like, don’t speed. Don’t text and drive. Pay attention to your surroundings. You would be wise to heed those instructions so that the car will run well (and so that you won’t find yourself stranded one day on the side of the road!).
With God’s good gift of sex, it makes sense to assume that the creator knows best–that the giver knows the gift. We shouldn’t expect the world to agree…it never has. Decades ago, C. S. Lewis wrote, “Poster after poster, film after film, novel after novel, associate the idea of sexual indulgence with the ideas of health, normality, youth, frankness and good humor. Now this association is a lie. Like all powerful lies, it is based on truth…that sex in itself (apart from the excesses and obsessions that have grown round it) is normal and healthy and all the rest of it. [But] for any happiness, even in this world, quite a lot of restraint is going to be necessary; so the claim made by every desire, when it is strong, to be healthy and reasonable, counts for nothing.” (C.S. Lewis, Mere Christianity, Page 100)
Genesis 1:27, 28 So God created mankind in his own image, in the image of God he created them; male and female he created them. God blessed them and said to them, “Be fruitful and increase in number; fill the earth and subdue it. Rule over the fish in the sea and the birds in the sky and over every living creature that moves on the ground.”
“But here’s the deal. God is the one who invented sex. It was his idea. He sees it a third way: There is more to love than sex. That’s true if you’re married or single, gay, straight, or somewhere in the middle. Saying ‘no’ to our sexual desires isn’t failing to live as our most authentic selves. It’s actually one way we love God and each other. Everyone alive – all of us – need to say ‘no’ to our sexual desires at times.” – Love Episode
“Each divine demand is really a summons into a transformative process in which we discover deeper levels of peace, joy, and fulfillment in God and in Christian love than we could otherwise have known.” ~ Timothy Keller, Sex, May 19, 2010