Biblical Answer

Sex is special in marriage because it is a physical expression of relational oneness and permanence. This is seen in the phrase "one flesh" which is a term that describes the intimacy of sex in marriage. The Bible teaches that sex is not just for physical pleasure, but also for spiritual purposes that serve to support and fulfill marriage and family duties. These purposes are fixed and never change, and are the same for everyone regardless of what a person thinks, feels, or chooses.

The specialness of sex in marriage is also tied to its ability to bring about spiritual maturity. When sex is viewed as a method that God invented to do whole-life entrustment and self-giving, it can lead to a deeper sense of connection and intimacy with one's partner. This is because sex is not just a physical act, but also a way of expressing love, commitment, and vulnerability. When sex is used in this way, it can bring about a sense of unity and oneness that is not just physical, but also emotional and spiritual.

In order for sex to be special in marriage, it requires a unique and relational context. This means that sex should not be seen as just a physical act, but as a way of expressing love and commitment to one's partner. It requires a sense of exclusivity and selflessness, which is eroded by sex outside of marriage. When sex is viewed as a way of serving one's partner and expressing love and commitment, it can bring about a sense of spiritual maturity and deepen the intimacy and connection between partners. This is what makes marital sex special.