Retaining Knowledge

There is a story of a learned man who came to visit a rebbe. The scholar was no longer a younger man - he was close to thirty - but he had never before visited a rebbe. "What have you done all your life?" the master asked him. "I have gone through the whole Talmud three times," answered the learned man. "Yes, but how much of the Talmud has gone through you?" the rebbe inquired.

(Rabbi Abraham J. Heschel)

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UPDATE: The Rebbe mentioned in this story was Rebbe Menachem Mendel of Kotzk. [Hat tip, Yitz]