This question is particularly appropriate in our time. Our post-Christian American culture has almost entirely moved away the God-given boundaries around human sexuality. What has developed in its place is “companionate sexual relationships,” even "companionate marriages," in which open relationships exist for which there are no real expectations of life-long intimacy or expectation of sacrificial, unconditional love. All that is required is mutual consent at the moment… no commitment, no binding mutual responsibility, always a back door to the relationship. Whether we like it of not, it is not what God willed for human sexuality and the family charged with procreationand and nurture of children.
God has in mind something much more grand than this for the marvel of human sexuality. Matrimony and the Marriage Bed offer a possibility for the most fulfilling of all human-to-human relationships. It offers the possibility for two people becoming “One Flesh,” blending their lives together and being more complete, healthy and whole than either of their lives separately could be. The union of a man and a woman is also intended by God for the procreation and nurture of children, and it is this stable family environment of unconditional, sacrificial love that is the God-intended setting for the raising of children. This in a nutshell was God’s intent in Creation (Genesis 2:4‑9, 15‑24). The marriage liturgy puts it this way: “The union of husband and wife in heart, body, and mind is intended by God for their mutual joy; for the help and comfort given one another in prosperity and adversity; and, when it is God’s will, for the procreation of children and their nurture in the knowledge and love of the Lord.”
Humans are made in the image of God and are therefore both physical and spiritual beings, and the mating of two people has physical and spiritual consequences. Human intercourse is a spiritual act. The spiritual consequence can be what psychologist call bonding or Peter Harobin in his teachings calls Soul Ties. These soul ties stay with us in life. Multiple ties have their affect on that one eventual life-long Soul Tie, denigrating it and interfering with it. God’s boundaries around sexuality, therefore, are there for a reason, a divine reason.