"Words Have the Power of Life and Death"

Our Rabbi’s teach that if a person is meritorious, his days are lengthened, but if not, they are reduced, G-d forbid. Rav Yosef Shani, shlit”a, of Yerusahalyim, once shared a family story that illustrates this idea most dramatically:
Years ago, on Erev Yom Kippur, one of the Rav’s uncles was forced by his employer to show up for work until mid-day. “I know that you would rather not come, but you won’t have to do anything,” the boss reassured him. “Just sit at the counter in case someone comes in, and you can go home early.”
So Rav Shani’s uncle assumed his post, and spent the entire morning immersed in Tehillim. During that period, Rav Shani’s grandmother had been very ill, and it appeared as though she might not live through the next day or two. As the Rav’s uncle recited Tehillim, his heart was with his ailing mother.
Just then, a stranger entered the store. “What are you doing?” asked the man.
“My mother is ill, it is just before the holiest day of the year, and I am reciting Tehillim.”
The stranger scoffed, “Do you think that those words are going to do any good? You might as well read names out of the phone book!”
The older man was astonished, “What, don’t you believe in anything?”
The customer proclaimed, “I only believe in what I can see.”
Feeling a sudden inspiration, the Rav’s uncle asked, “If I pay you one British pound, will you sell me ten years of your life?”
The other man laughed, “You’ll pay good money for a fantasy? I’ll give you ten years of my life for that pound, and tonight while you’re fasting, I’m going to buy myself a bottle of Arak (spirits) and make a party!” The two signed a short contract and dated it. Then the man bought what he needed and left.
By the time Sukkos passed, Rav Shani’s grandmother had recovered, and everyone forgot about the incident.
Many years later, Rav Shani’s uncle himself passed away, and after the shloshim, the family went to dismantle his apartment. Lodged in a crevice in a closet, they discovered a slip of paper—and remembered that their grandmother had passed away exactly ten years after that fateful Erev Yom Kippur!