NOTES for Mar 10:1-16
Christ's words about marriage and marital unity can be understood only in the context of the relationships of the Kingdom. The foundation here is God's design for the union of man and woman, reflected in the Book of Genesis in the account of the creation of the human being. There the union of man and woman, the marital union, is considered not simply one element of human life, but a new quality of that life. It is irreversible in the same sense that every qualitative spiritual change in a person's life is irreversible: it cannot simply be "rolled back" by returning to what existed "before."
Of course, one can reject this new quality, one can ignore it, one can do everything possible to reduce its consequences to zero, but one cannot again become the same person one was before the change. In relations between a man and a woman, on the physiological level this corresponds to the impossibility of returning to a virginal state once virginity has been lost.
A divorced man is not the same as an unmarried man, just as a divorced woman is not the same as an unmarried woman. The issue here is not only the experience of family life, but also the fact that human nature has changed, and changed irreversibly. At the same time, it does not matter at all what the two people living together think about their shared life. They may think that everything between them is temporary, that they have decided only to "try it out," that they need nothing except sex. In the same way, spouses who are divorcing after living a long life together may think that "everything is over" between them. In reality, however, once relations between a man and a woman have begun, they can never end.
They are for all eternity, whatever he and she may have thought when they came together, grew close, and began a life together, whether forever or for one night. The only question is what the quality of these relations will be, how they will eventually be transformed, and what they will finally become. Once established, they will remain forever, and only the two who established them can decide before God and together with Him what to do with them in the fullness and eternity of the Kingdom.