The NT Greek word for “mystery” means “secret” and when used by the Apostle Paul refers to one long-hidden but now revealed. Paul was not a keeper of Divine secrets but rather a dispenser of those revealed to him by God for the benefit of churches.
Spiritually, Paul’s letter to the Ephesians is one of his deepest, but lest his readers think of it as purely mystical, the Apostle applies spiritual truths to practical problems.
In Ephesians, chapter 5, Paul describes Jesus as “the Saviour of the body” and applies this to the duty of husbands to love their wives “even as Christ also loved the church and gave himself for her, that he might sanctify and cleanse her with the washing of water by the word”.
In other words, Christ loves the church and cares for it as a husband loves and cares for his wife. This may raise the hackles of rabid feminists, but those were male-dominant days, and husbands were responsible for their wife’s health and wellbeing, which every loving, caring married man is still.
“That he might present her to himself [as] a glorious church, not having spot or wrinkle, or any such thing, but that she should be holy [spiritually clean] and without blemish. So, husbands ought to love their own wives as [they would] their own bodies; he who loves his wife loves himself. (Eve was made from the DNA in the bone marrow of Adam’s rib.) For no man ever hated his own flesh, but nourishes and cherishes it, just as the Lord does the church.”
Paul then goes deeper. He writes: “For we are members of his body, of his flesh and of his bones.” Paul relates this to marriage. “For this reason, a man shall leave his father and his mother and be joined to his wife, and the two shall become one flesh.”
But there’s more! “This is a great mystery, but I speak concerning Christ and the church.” The Apostle closes with “Nevertheless”. In using this word, he applies the mystery to the reality of married life (about which there are more realities than mysteries). “Nevertheless, let each one of you in particular so love his own wife as himself; and the wife should respect her husband.”
Which she probably will, if he does.
Paul’s spiritually-deep letter begins with statements of Who and What and Where we are in Christ positionally, and ends with applying the heavenly truths in these things to down-to-earth practicalites. Who says that Christians are “too heavenly minded for any earthly use”?
Certainly not Paul the Apostle!