I'm currently reading The Meaning of Marriage by Timothy Keller & I especially loved this paragraph:
"Marriage is God's gift to the church. Through Christian marriages, the story of the gospel - of sin, grace, and restoration - can be seen and heard both inside the church and out in the world. Christian marriages proclaim the gospel. That is how important they are. The Christian community has a deep interest in the development of strong, great marriages and therefore a vested interest in the community's singles marrying well."
I liked this one, too. It made me think of the handful of married couples I admire who have shown me this:
"We are called to be transparent before one another. One particular way married people can do that is by displaying the real work of their marriages - not just the sweet, light parts...but the hard, embattled parts - to the unmarried. Think of what an impact that would have! Singles must see how hard and how glorious marriage is, not just how satisfying it is. They only way that happens is if married couples share their lives with singles so they can understand what marriage is really like."