What does 'one flesh' mean in Genesis 2:24?

"One flesh" is more than a poetic description of physical union. The vocabulary Genesis 2:24 uses to describe it is covenant vocabulary.

Here is the verse:

"Therefore a man shall leave his father and his mother, and cleave to his wife, and they shall become one flesh." — Genesis 2:24

The word behind "cleave" is דָּבַק (davaq). It's a strong-adhesion word — the kind of bond where two things become effectively inseparable. The Psalms use it for a tongue stuck to the roof of a parched mouth (Psalm 22:15). Job uses it for the scales of the sea-monster Leviathan, locked so tight "they cannot be separated" (Job 41:17). The image is permanent, not tentative.

But here is what the Old Testament does with davaq most consistently: it is the word for Israel's covenant loyalty to Yahweh.

"You shall fear Yahweh your God; you shall serve him, cleave (davaq) to him." — Deuteronomy 10:20

Deuteronomy 11:22 and 30:20 repeat the instruction. Ruth 1:14 uses it for Ruth's refusal to leave Naomi — "Ruth cleaved to her" — which is one of the Old Testament's most moving portraits of covenant faithfulness between two human beings. The same verb.

So when the narrator in Genesis 2:24 says a man shall davaq to his wife, he is choosing the word that Israel will later use for clinging to Yahweh when everything pulls in the other direction. Marriage is not merely a social arrangement; it is described in the language of covenant.

The Greek translation (the Septuagint) renders davaq in Genesis 2:24 with the verb προσκολλάω (proskollaō) — "to glue to." And the Septuagint adds something the Hebrew doesn't have: the words "the two" (οἱ δύο, hoi dyo). The Hebrew says "they shall become one flesh"; the Septuagint says "the two shall become one flesh."

Every time the New Testament quotes Genesis 2:24, it follows the Septuagint's "the two" — not the bare Hebrew:

• Jesus in Matthew 19:5 and Mark 10:8 (in the divorce discussion)
• Paul in 1 Corinthians 6:16 (arguing that sexual union always creates a one-flesh bond)
• Paul again in Ephesians 5:31 (drawing the analogy between marriage and Christ and the church)

Four New Testament writers, four quotations, the same Septuagint form every time. The "one flesh" of Genesis 2:24 is the verse the New Testament keeps returning to when it wants to say something definitive about marriage, the body, and the union of Christ with his people.

The full study on Genesis 2:4–25 traces all 54 Old Testament occurrences of davaq, the textual difference between the Hebrew and Septuagint at Genesis 2:24, and why Paul's quotation in Ephesians 5 calls the one-flesh union "a great mystery."