Therefore a man shall leave his father and mother and hold fast to his wife, and the two shall become one flesh. This mystery is profound, and I am saying that it refers to Christ and the church. (The Apostle Paul in Ephesians 5)
Off the topic of marriage, but I couldn't resist linking to this excellent series of articles on youth ministry. They point out a lot of issues that I've thought for a long time but haven't put into writing. It's amazing to me how sacred youth groups are to churches when they have so little fruit on the tree long term.