What does the Bible say about sex?

By Sean Doherty

The classic Christian view is that sex should be within marriage, and that marriage is the union of one man and one woman. In order to understand why, we need to explore what the purpose of sex is, according to the Bible.

Sex has two purposes. The first is obviously procreation. However, it is important not to imply that procreation is the only purpose of sex. First, this is true because many marriages are childless. A few are childless through choice, but most are childless because of infertility. But that does not make them bad marriages! And on the flip side, there are many kinds of sexual union which can result in procreation, but which are deeply harmful and wrong (such as rape, adultery and incest). Objections to same-sex sexual relationships solely on the grounds that they can never be procreative therefore do not succeed. There must be more to sex than procreation.

There must be more to sex than procreation

And this is exactly what we find in the Bible. As well as giving the gift of sex to be the means of procreation, God also gives it as a gift which brings husband and wife together into a physical union (‘the two shall become one flesh’, Genesis 2:24). This physical intimacy expresses and strengthens the bringing together of their lives. So, according to the Bible, sex has two purposes: not just procreation, but also delight and intimacy.

...sex has two purposes: not just procreation, but also delight and intimacy

But why must this be restricted to marriage? The answer the Bible gives is that the one-flesh union of husband and wife is a symbol and reflection of two things.

1) Marriage reflects the relationship between the persons of the Trinity 

Genesis 1:27 says:“So God created human beings in his own image,in the image of God he created them; male and female he created them.” (TNIV)

The difference between women and men is the way humanity reflects or represents God. The Father and the Son and the Spirit are all fundamentally different to one another, and yet fundamentally united to one another. God is not a solitary individual, but a relational, interdependent being. And at our most fundamental level, we reflect that.

2) Marriage reflects the relationship between Christ and the church

Read Ephesians 5. Once again, the difference between these two is real and cannot be downplayed, but their union is also real.

This is why sex must be between people who are fundamentally (or ‘ontologically’) different to one another in the way that men and women are fundamentally different to one another. Sex within marriage shows that people who are truly different also can be truly united. (This is also why marriage must be a permanent union.) The Father and the Son and the Spirit are all fundamentally different to one another, and yet fundamentally united to one another. Christ and the church are also different to each other, yet truly brought together as one. It is not enough to be different people, different individuals. The people must be different genders. In fact, sex uses precisely the physical differences between a woman and a man in order to unite them physically.

The people must be different genders

So, sex must be between a man and a woman for exactly the same reason that it must be within a permanent relationship. The point of sex is not simply to unite any two individuals, but to show that there can be union between two people who are fundamentally different, just as Christ and the church are fundamentally different but truly united, and just as Father, Son and Spirit are different and yet truly one. The purpose of sexual intimacy within God’s good creation is to unite those who are different in a lifelong covenantal relationship. That is why God created sex.