Marriage and the Mystery of Christ and the Church
Ephesians addresses wives and husbands within the preceding call to Spirit-filled life and submission. Husbands receive an especially extensive command: love their wives as Christ loved the church and gave himself for her, nourishing and cherishing rather than exploiting. Paul describes Christ sanctifying and cleansing the church with “the washing of water by the word,” then quotes Genesis 2:24—two becoming one flesh—and declares that the mystery is great because he is speaking about Christ and the church.
Where this fits in the story: this is one of Ephesians’ clearest “Old concealed / New revealed” moments. Genesis speaks truly about human marriage in its creation setting; Ephesians does not erase that meaning but reveals a larger canonical dimension in which one-flesh covenant union is applied explicitly to Christ and his church. The washing language likely evokes Christian baptism and also fits the bridal-bath image of a bride prepared for her husband.