This fits well with that which follows (“they two shall be one flesh”). Our English cannot well express the Greek in good sense word for word, which is thus, “they two shall be into,” or “in one flesh.” The meaning is that they which were two before marriage, by the bond of marriage are brought into one flesh, to be even as one flesh, as closely united, as the parts of the same body, and the same flesh. This unity is not through sexual intercourse (for if they be married they are one flesh, though they never know one another sexually), nor through procreation, because one child comes from them both (for though they never had a child, yet are they one flesh), but in regard of God’s institution, who has set it down for a law, and as another nature, that man and wife should be so close to one another. Their consent in marriage (by virtue of God’s institution) makes them to be one flesh.

William Gouge, Building a Godly Home: A Holy Vision for Family Life, 134-135.