A Blessing for a Son
Some acquaintances from Holon once came to Rav Shmuel for advice about buying a plot of land for a shul. He traveled from Yerushalayim himself to look for a suitable place. They found a man who did not keep Torah and mitzvos and who owned a fitting plot, and the Rav asked him to sell it at a good price for the sake of the higher purpose.
The man answered, "I am willing to lower the price, provided that the Rav blesses me with a son. I am no longer young, and I have never had a son." The Rav replied, "For the blessing to take hold, you must keep Shabbos, because Shabbos is the source of blessing."
The man agreed to the Rav's condition, saying that he would begin to keep Shabbos in two weeks. But from that moment on, he stopped desecrating Shabbos. And he was granted a son, as the Rav had told him.