Matthew 19:9

9. Except it be for fornication Our Lord here indicates no new law. He does not even restore the old one. He simply declares what has always been the law of God. Moses, in his civil code, declined to enforce the strictness of the moral law. Unlawful intercourse with any other person breaks the marriage tie. The criminal has deserted forever the marriage partner, and has become unfit for further association. Impure and outcast, the guilty being can never again enter a pure and lawful marriage covenant.

The orderly family is the foundation of the orderly society. Wherever marriage is lightly esteemed there is great danger that every tie will become loose. Unless the law be strong and strict enough to silence and suppress the roving imagination and roving desire, and to settle completely all thoughts of breaking or overstepping the sacred limit, disorder, licentiousness, and moral anarchy commence. A sensual tone pervades the life. And it is a universal law that where sexual license prevails, lawlessness of every other kind prevails. Lust and cruelty ever go together.