The Greek text of verse 31 is composed entirely of the quotation of Genesis 2.24; there are no introductory words. Good News Translation, for clarity, has added As the scripture says (see also New English Bible, Translator’s New Testament). Since in so many languages one cannot speak of the Scriptures “saying something,” one may need to change As the scripture says to “As one can read in the writings” or “As one can read in the Holy Writings.”
The phrase which begins the quotation, For this reason, differs in the Greek text here from the Septuagint of Genesis 2.24 but has the same meaning. In this context the phrase has no clear meaning and is used only because it is part of the text cited. As Robinson remarks, Genesis 2.24 is quoted to justify the statement of the writer of Ephesians that a man who loves his wife loves himself. Barth says that “for this reason” introduces the rest of the quotation from Genesis 2.24, because the relation of Christ to the church is the fulfillment of what Genesis 2.24 says about a man becoming one flesh with his wife. This seems quite fanciful.
Because of the fact that the phrase For this reason does not point specifically to some previous statement in the text of Ephesians, it may be more satisfactory to use a somewhat more general transitional phrase or word, for example, “accordingly” or “so.”
The compound verb translated unite occurs elsewhere in the New Testament only in Mark 10.7 (where Gen 2.24 is also quoted; in the quotation in Matt 19.5 the simple form of “unite” is used; it is also used in 1 Cor 6.16, 17, where Paul also quotes from Gen 2.24). The word has a definite sexual dimension, alluding to the sexual union of husband and wife; in 1 Corinthians 6.16 Paul uses the simple form of the verb in the same sense of a man having intercourse with a prostitute.
In translating the statement a man will leave his father and mother one must avoid the implication of “desert” or “abandon.” Will leave his father and mother can often be best rendered as “will leave the home of his father and mother.” Or else in some languages it may be necessary to say “For this reason a man’s primary relationship (or, responsibility) is no longer with his father and mother, but with his wife. When he marries, he and his wife become one.”
Good News Translation the two will become one translates the Greek “the two will become one flesh” (see Revised Standard Version). It may be impossible to translate the two will become one, especially if the predicate numeral “one” must show plural agreement with the subject. Therefore it may be necessary to translate this by “the two will become like one person.”
Quoted with permission from Bratcher, Robert C. and Nida, Eugene A. A Handbook on Paul’s Letter to the Ephesians. (UBS Handbook Series). New York: UBS, 1982. For this and other handbooks for translators see here .