The moral of this story is: Just as the endless running water makes the pond so clear, people's minds can become more open-minded and keen by constantly reading and absorbing new knowledge.
3. The condensed idiom is: Yu Gong Yi Shan.
(with two questions:
1. condensed into a famous saying: sensible science, human feelings practice.
2. Modern articles: "The Enlightenment of Dripping Water wears away the Stone" (Jiangsu Education Press, Book 10 of Chinese).