If it is to be imbued with sanctity, the couple's love must be free of selfish interests for personal gain. When we associate with another individual and cultivate his friendship only for our own benefit, we act out of love for ourselves, not out of affection for another. 

It is important to stop and consider this basic question: Is the bond of love between husband and wife indeed not composed, at least partially, of a desire for personal benefit? Don't people decide to marry in order to satisfy their own emotional and physical needs?

To resolve this seeming contradiction, let us refer to the words of one of the classic sages, Nachmanides, (often called “the Ramban”, and acronym of his name). The Ramban composed a monumental commentary on the Five Books of Moses. In Genesis, he analyzes one of the verses describing the first marriage, that of Adam and Eve:

Therefore, a man shall leave his father and his mother, and cling to his wife. (Genesis 2:24)

The Ramban points out that the Scripture does not state merely that “A man shall leave his father and his mother...”  but prefaces the statement with the word “Therefore ...”  From here we learn that there is a reason that a man leaves his parents and his home, and forms a new, even stronger bond with his wife. Something compels him to take this step. What is it?

The Ramban refers us to the account of the creation of Eve, the mother of all mankind. When first created, Adam and Eve were one, not only spiritually, but also physically. It was only afterward that G-d separated them physically so that they became two separate individuals. The act of separating them physically did not terminate the spiritual bond between them. On the contrary, it enhanced it. As we say in English, “Absence makes the heart grow fonder.” 

Following his separation from Eve, Adam felt a lack which he longed to fill. He missed his soul-companion, who was a part of himself. Without Eve, he was not complete. He longed for a companion who would be “bone of my bone, and flesh of my flesh.” 

This inner yearning for belonging and companionship was part and parcel of the hereditary human make-up which Adam passed on to his descendants. We expect a newborn baby to have two arms and not three, two ears, and not one, following the pattern established by Adam thousands of years ago, because that is how Man was originally fashioned. 

Similarly, we anticipate that when that infant matures, he or she will be impelled to leave the family nest and establish a home of his/her own. It is because of this inner stirring, inherited from Adam himself, that one is willing to leave behind even those who have always been his or her closest relatives and to set out with one's spouse to establish an independent family unit of his own.

Logic would dictate that the bond to parents be deeper than that to a spouse. How much time, effort and money have the father and mother invested in caring for and raising their child! The best, most productive years of their lives were devoted to caring for their offspring. Nonetheless, we take it as only “natural” that each child, in turn, leave the home which has meant so much to him or her, to form a new, even stronger bond. The Ramban teaches us that the bond of matrimony is so overwhelmingly strong because, in essence, husband and wife were originally one entity, just as were Adam and Eve when G-d first created them.