Dietrich Bonhoeffer in bold fashion comments on Genesis 2:24 that "the narrator is obviously stumbling". This is one of many bold and enlightening sections of his book, Creation and Fall, Temptation: Two Biblical Studies, and one that is foundational to the so-called 'biblical definition of marriage'. My mouth is left gapping the audacity of Bonhoeffer's words and even more so at my inability to answer this statement.
Therefore a man [Mann] leaves his father and his mother and cleaves to his woman [Weib], and they become one flesh.
It could be said that here the narrator is obviously stumbling. How can Adam, who knows nothing of a father or a mother, say such a thing? We could also say this is the narrator's practical application of the story, or something of the kind. Really, though, we recognize a basic fact here which has so far been hidden and which has now, as it were unintentionally, come to light.
We ourselves are the Adam who speaks. We have a father and a mother and we know the uniqueness of belonging to one another in the love of man and woman, but for us this knowledge has been wholly spoiled and destroyed by our guilt. This passage does not justify running away from the worldly order or from our connection with our father and mother. It is the profoundest way possible of describing the depth and seriousness of belonging to one another. This ultimate belonging to one another is undoubtedly seen here in connection with man's sexuality. Very clearly sexuality is the expression of the two-sidedness of being both an individual and being one with the other person. Sexuality is nothing but the ultimate realization of our belonging to one another. Here sexuality has as yet no life of its own detached from this purpose.
Here the community of man and woman [Mann und Frau] is the community derived from God, the community of love glorifying and worshiping him as the Creator. It is therefore the Church in its original form. And because it is the Church [Kirche] it is a community eternally bound together. For us such statements do not imply the glorification of our marriages; they are the indication that for us at any rate the connection between man and woman is not such an unequivocally real one and that the Church's action in the marriage ceremony is perhaps the most questionable of all the Church's official actions.
The community of love has been torn to pieces by sexuality and become passion [Sucht]. Therefore it affirms itself and denies the other person as God's creature. This community rests upon the claim that the one makes upon his share in the other-upon his rib in the other, upon the other's having his origin in him. This community is plainly not the glorification of the Creator-in which the Creator once again does the work of his creation upon the unknowing, sleeping Adam and Eve. It is man's snatching for himself the strength and the glory of the Creator-the ascent of man to unconscious awareness [bewußtlosen bewußtheit] of his own ego, to begetting and giving birth out of his own power, in the waking of drunkenness [im Waschsein des Rausches]. Of course, tills abysmal destruction of the original state does not abolish the fact that, in the truest sense, the community of man and woman [Mann und Frau] is intended to be the Church (Eph 5:30-32).
Dietrich Bonhoeffer, Creation and Fall, Temptation: Two Biblical Studies, pg62