When a couple speaks their vows, it is not a man or a woman or a pastor or parent who is the main actor – the main doer. God is. God joins a husband and a wife into a one-flesh union. God does that. The world does not know this. Which is one of the reasons why marriage is treated so casually. And Christians often act like they don’t know it, which is one of the reasons marriage in the church is not seen as the wonder it is. Marriage is God’s doing because it is a one-flesh union that God Himself performs.
John Piper