The Talmud relates an incident about Rav Prada, who was the leader of his own generation. Rav Prada had a certain student who was very slow to grasp a concept. But, far from giving up on him, Rav Prada sat with this boy day after day and tirelessly repeated the lesson for him until he learned it. He would repeat the lesson no less than four hundred times until his pupil knew the subject. One day he had already repeated the lesson four hundred times, and yet, the boy still hadn't grasped it. What was Rav Prada's reaction? Certainly he must have thrown up his hands and concluded that this child was simply too slow to learn. But, no, Rav Prada began again and taught the lesson another four hundred times!
That day a heavenly voice spoke to Rav Prada. Because of his tremendous patience and his devotion to his student's Torah learning he was given the option of choosing his reward. Either he could chose to have extraordinarily long life, or he could chose to benefit his entire generation by giving them all a portion in the World-to-Come.
It is obvious what a Tzadik like Rav Prada would chose. Of course, he decided to share his reward with all of his fellow Jews, and all the Jews of that generation received a portion in the World-to-Come.
