There are two levels at which the glory of God may shine forth from a Christian marriage:
One is at the structural level when both spouses fulfill the roles God intended for them — the man as leader like Christ, the wife as advocate and follower of that leadership. When those roles are lived out, the glory of God's love and wisdom in Christ is displayed to the world.
But there is another deeper, more foundational level where the glory of God must shine if these roles are to be sustained as God designed. The power and impulse to carry through the self-denial and daily, monthly, yearly dying that will be required in loving an imperfect wife and loving an imperfect husband must come from a hope-giving, soul-sustaining, superior satisfaction in God.
I don't think that our love for our wives or theirs for us will glorify God until it flows from a heart that delights in God more than marriage. Marriage will be preserved for the glory of God and shaped for the glory of God when the glory of God is more precious to us than marriage.
Excerpted from John Piper, "The Surpassing Goal: Marriage Lived for the Glory of God," Building Strong Families, (Wheaton: Crossway, 2002). 96.