Faith

"When God told Abraham, who was a hundred at the time, that at the age of ninety his wife, Sarah, was finally going to have a baby, Abraham came close to knocking himself out—'fell on his face and laughed,' as Genesis puts it (17:17). In another version of the story (18:8ff.), Sarah is hiding behind the door eavesdropping, and here it's Sarah herself who nearly splits a gut—although when God asks her about it afterward, she denies it. 'No, but you did laugh,' God says, thus having the last word as well as the first. God doesn't seem to hold their outbursts against them, however. On the contrary, God tells them the baby's going to be a boy and they are to name him Isaac. Isaac in Hebrew means "laughter."

Why did the two old crocks laugh? They laughed because they knew only a fool would believe that a woman with one foot in the grave was soon going to have her other foot in the maternity ward. They laughed because God expected them to believe it anyway. They laughed because God seemed to believe it. They laughed because they half believed it themselves. They laughed because laughing felt better than crying. They laughed because if by some crazy chance it just happened to come true, they would really have something to laugh about, and in the meanwhile it helped keep them going.

Faith is 'the assurance of things hoped for, the conviction of things not seen,' says the Letter to the Hebrews (11:1). Faith is laughter at the promise of a child called Laughter."

Frederick Buechner, from Wishful Thinking: a Seeker's ABC

http://frederickbuechner.com/content/faith