Forty Days of Torah in Heaven

Rav Mordechai of Chernobyl once said that his father, Rav Nachum of Chernobyl, used to appear to him every night, after Rav Nachum had left this world, to study with him. Suddenly, for forty days, his father did not come.

When Rav Nachum began to appear again, Rav Mordechai asked why he had not come for forty days. Rav Nachum answered that Rav Dovid of Lelov had passed away in Poland, and it had been announced in Heaven that Rav Dovid would give a shiur for forty days and nights straight. He had not wanted to miss anything.