And they two shall be one flesh. They shall be one man, or, to use a common phrase, they shall constitute one person; which certainly would not hold true with regard to any other kind of relationship. All depends on this, that the wife was formed of the flesh and bones of her husband. Such is the union between us and Christ, who in some sort makes us partakers of his substance. “We are bone of his bone, and flesh of his flesh,” (Gen. 2:23;) not because, like ourselves, he has a human nature, but because, by the power of his Spirit, he makes us a part of his body, so that from him we derive our life.

John Calvin, Commentaries on the Epistles of Paul to the Galatians and Ephesians, trans. William Pringle (repr. Bellingham, WA: Logos Bible Software, 2010), 324.