The first, and perhaps most important human relationship described in scripture is marriage; it’s introduced immediately after Man and Woman are created and it’s oriented in the husband’s responsibility to “cleave unto his wife”. (Ge 2:24) What does this mean?
This leaving is evidently inherently both physical and spiritual; physical in the sense that each man is to have his own house, a dwelling where he cares for and protects himself and his family. (De 22:2) To do so effectively he must first learn to care for and provide for himself: have an occupation, a means of generating value, and become productive and proficient in his work. (Pr 24:27)
This leaving is also spiritual in the sense that the man is to be recognized by other men, particularly by his own father, as a man, received and understood by others to be an independently functioning, responsible member of society. In many cultures this is marked by a special ceremony where a boy, having demonstrated the necessary skills to provide for himself, participates in a ritual, after which his father acknowledges his manhood and receives him as an equal among other men.
Once a man leaves his parents and takes a wife, one given him by God as a suitable helper (Ge 2:18) in pursuing a unique destiny together (Ge 2:28), he becomes one flesh with her; husband and wife experience a metaphysical union and become part of a single human organism, permanently interconnected, members one of another. (1Co 6:16) It is in this context that the husband is to — cleave unto his wife.
The immediate context then informs us that this cleaving relates to an orientation in the man which initiates, encourages, facilitates and promotes an ongoing pattern of interaction with his wife which enables them to seamlessly live and work together to overcome the challenges they will inevitably face in pursuing their mutual destiny. It is a joining of his mind, soul and heart with his wife such that the two of them are thinking and acting together more and more as one; in the same way the two have become one flesh, the goal is to be of one heart, one mind, and one soul. (Ac 4:32)
This marital union is intended to produce a single metaphysical being capable of achieving what neither of the two could ever accomplish on their own, and the man is to lead and manage their interactions so as to produce this type of unity in his marriage.
God has called Man to this most complex and difficult task of cleaving to Woman, a unique and separate individual bearing the image of God, and necessarily very much unlike himself. Their differences, their unique orientations, inclinations and capabilities, are an intrinsic part of this design, enabling and strengthening the union they are to produce together. This mysterious process is, in itself, the work of God, the shadow of an eternal, heavenly marriage between God and Man. (Ep 5:31-32)