Biblically speaking, relationships are more central to our being than bodily pleasure. We are first of all relational beings. God made humans male and female (Gen 1:27), addressed Adam as a covenant-partner (Gen 2:16-17), and made Eve as a suitable helper for Adam, for whom it was not good to be alone (Gen 2:18). Abraham was to be the channel for God's blessing to flow to all the families of the earth (Gen 12:3). Christ died and rose for his people - the church (Eph 1:22, 2:19-22, etc) who are to mutually encourage each other (Gal 6:2; Heb 10:24-25). We are to use our bodies to enhance relationships. If we are in healthy relationships, our bodies will prosper. If we are in unhealthy relationships, our bodies will deteriorate.
Relationships are built on trust, and trust is built on the reliability of a person’s character, usually expressed in their faithfulness to promises. This is because relationships are essentially other-focused.
In any intimate relationship – family, spouse, BFF – we take the risk of giving ourselves to the other person, and acting for their benefit, without protecting ourselves – that is to say, we love them. We trust our relational partner, that they, recognising and valuing this gift of ourselves, will cherish and protect us – we trust that they will respond to, and value, our love. We also trust that they will return our love with a commensurate gift of themselves – that they will give themselves to us, and act for our benefit, without concern for themselves – that is to say, that they will love us in return.
This is why relationships are both risky and rewarding. In any relationship, we make ourself vulnerable to our relational partner. If they return our love, then we rejoice and flourish, for our self has been affirmed by the one to whom we entrusted it. If they do not return our love, then we are crushed, for we have given our selves to another, and they have not deemed it worthy of response, but have discarded it.
Sexuality fits into this relational framework. Our sexuality is a good bodily function, given to us by God, to enhance our relationships. Sexual activity brings physical bodies and relational love together. Love and sex are mutually reinforcing: when we fall in love with someone, we desire sex with them; having sex with someone reinforces our love for them. In sexual activity, we make our bodies vulnerable, giving them to each other for mutual pleasure. Betrayal by our sexual partner has deep emotional and psychological consequences.
This is why the Bible presents marriage as the proper context for sexual activity. In a marriage, a man and a woman promise to commit to each other for life. Those promises define the relationship between the two of them, and call them both to mutual faithfulness – to have the personal character to be faithful to those promises, whatever difficulties life may throw at them. Having promised faithfulness to each other, they entrust their bodies to each other in sex.