The Zchus Of A Mitzva

Rav Eliyashiv Shlita was born [about 100 years ago!] after his mother was childless for 17 years. He related that his parents had been to a doctor who told them that they have no chance to ever have children. She lived at the time with her husband at her father-in-laws home. Her father-in-law was the famous mekubbal and author of the sefer "Leshem" [known as the "Baal Haleshem"]. After hearing the sad news she wanted to come home and cry but didn't want to disturb the holy Ba'al Ha'Leshem's learnning. So she hid behind the horse stable and cried. Just then the Ba'al Ha'Leshem walked by. He asked her what was wrong. She replied that the doctor had told them that she will not be able to have children. "So why didn't you come inside?" he asked. She explained that she didn't want to interrupt his learning.

"In the merit of not interrupting my learning you will merit a son who will light up the whole world with his Torah and nobody will interrupt his learning."

And so it was.