What is the meaning of "one flesh"?

What is the meaning of "one flesh"?

This was God’s intention at the institution of marriage (Genesis 2:24). It expresses the oneness of a married couple. In this seminal statement, the Lord points out that a man leaves his role of obedience to his parents (although still responsible to honor them, Exo 20:12) to assume headship of a new and distinct relationship. At marriage a new family unit exists that had never existed before. This newly-formed oneness, involves a physical union, the culmination of marriage, but it involves more than that. Four of the five New Testament passages that refer to "one flesh" (Matthew 19:5, 6; Mark 10:8; Ephesians 5:31), quote the original statement and are passages that teach about marriage. The fifth (1 Corinthians 6:16) is part of Paul’s teaching about fornication (v 18). He states that one who "is joined to an harlot" is "one body." Then he cites the Lord’s original intention (Genesis 2:24) regarding "one flesh." The promiscuous relationship with a harlot is a physical union, but not the physical union God intended in marriage. "One body" does not include the intended intimacy and oneness of a unique relationship within marriage. "One body" is merely an external relationship. "One flesh" is both physical and relational, expressing the inseparable closeness of Christ and His Church (Ephesians 5:31, 32). This can never be expressed outside marriage.

D. Oliver