A man shall leave his father and his mother.  In a culture of strong bonds between the generations, this is striking.  A man’s primary human relationship is no longer with his parents or ancestors.  He breaks away from them for the sake of a more profound loyalty; and hold fast to his wife. 

A man, in marrying, enfolds his wife into his heart.  He rejoices to identify with her: “This at last is bone of my bones and flesh of my flesh” (verse 23).  At every level of his being, he becomes wholeheartedly devoted to her, as to no other; and they shall become one flesh.  “

"One flesh” is essential to the biblical view of marriage.  It means, one mortal life fully shared.  Two selfish me’s start learning to think like one unified us, sharing one everything: one life, one reputation, one bed, one suffering, one budget, one family, one mission, and so forth.  No barriers.  No hiding.  No aloofness.  Now total openness with total sharing and total solidarity, until death parts them.  Moreover, Jesus explained that, behind the word “become,” God is there: “What therefore God has joined together . . .” (Matthew 19:6).  He also made it clear that the word “they” in Genesis 2:24 means “the two” (Matthew 19:5), thus establishing one man/one woman as the biblical norm.  What we see then, is that marriage is not a product of human social evolution; marriage came down from God.  And he defined it for us.  He has the right to.  It belongs to him.