Question: "What does it mean that "the two shall become one flesh" (Genesis 2:24)?"
Answer: Genesis 2:24 gives us a picture of the marriage bond before sin entered the world: “Therefore a man shall leave his father and mother and be joined to his wife, and they shall become one flesh” (Genesis 2:24, NKJV). “One flesh” echoes the language of the preceding verse when Adam first meets Eve and exclaims, “This one is bone of my bone, and flesh from my flesh!” (Genesis 2:23, NLT). Two becoming one in marriage involves uniting two whole and separate people into a new, God-designed and God-purposed life.
The two shall become one flesh clause expresses the original purpose of marriage: to seal a permanent relationship between a husband and wife. Jesus spoke of this union in a conversation with the Pharisees about divorce: “But at the beginning of creation God ‘made them male and female. For this reason a man will leave his father and mother and be united to his wife, and the two will become one flesh.’ So they are no longer two, but one flesh. Therefore what God has joined together, let no one separate” (Mark 10:6–9; see also Matthew 19:4–6).
Marriage was intended to be an unbreakable, lifelong union. Termination of marriage in divorce was not considered before sin came into the world (Genesis 3). The Bible teaches that all instances of separation and divorce were because of sin (Deuteronomy 24:1–4; Ezra 9—10; Malachi 2:14; Matthew 5:31–32; Luke 16:18). When God said, “And the two shall become one,” His ideal objective was for the man and woman to join together in an inseparable and exclusive union.
Husbands and wives become “one flesh” in sexual intimacy, as reflected literally in their children’s lives. A child is one, new, whole, individual and separate life created through the physical union of two people—a man and a woman. God’s idyllic design for the sexual union in marriage is to be exclusive: “Give honor to marriage, and remain faithful to one another in marriage. God will surely judge people who are immoral and those who commit adultery” (Hebrews 13:4, NLT; see also Ephesians 5:22–33; 1 Timothy 3:2, 12 and Titus 1:6).
Two becoming one in the sexual aspect of marriage means caring for and fulfilling one another’s physical needs with respect and mutual consent (1 Corinthians 7:1–5), not exploiting one another (1 Thessalonians 4:3–7), and delighting in one another (Proverbs 5:15–19; Ecclesiastes 9:9). God’s design for physical intimacy in marriage is portrayed with beauty and dignity in the Song of Solomon.
Of course, oneness in marriage reaches far beyond the physical level. The original Hebrew word translated as “flesh” refers to much more than a person’s physical or sexual composition. It relates to the whole human existence. The biblical view of “one flesh” communicates a unity that covers every facet of a couple’s joint lives as husband and wife. In marriage, two whole lives unite together as one emotionally, intellectually, financially, spiritually, and in every other way. The “two shall become one” in purpose. They are so close that they function like one person, balancing each other’s strengths and weaknesses so that together they can fulfill their God-given calling.
In Scripture, marriage is viewed as a covenant relationship between a man and a woman (Malachi 2:14–16; Proverbs 2:16–17). The two people become dependent on each other and responsible for one another. This human bond in marriage is a metaphor for God’s relationship with Israel (Ezekiel 16:8) as well as a picture of the union between Christ and the church: “But whoever is united with the Lord is one with him in spirit” (1 Corinthians 6:17; cf. Ephesians 5:31–32).
Nevertheless, since the fall of humankind, the marriage relationship has failed to measure up to its God-intended ideal. Apart from salvation in Jesus Christ and the Holy Spirit’s sanctifying work, husbands and wives cannot even begin to live in mutual harmony and accord. Yet, in Christ, believers discover the unconditional love of God (1 Corinthians 13:4–8)—a supernatural love that enables them to make a lifelong commitment to care for their spouse as Christ loved His bride, the church, and sacrificed Himself for her (Ephesians 5:25).
The two shall become one flesh expresses the heart of the Bible’s conception of marriage. By entering into marriage, a husband and wife take solemn vows to become permanently one flesh—to love, honor, and cherish one another until they are parted by death.