Near the end of his life, Rabbi Eliezer ben Hyrcanus lay on his sickbed and pressed his disciples with a strange complaint. Had you come to study with me during these last years, he said to colleagues who had stayed away during his excommunication, you might have added much to your knowledge of Torah. Now that knowledge will perish with me.
I learned much in my time, he went on, and I taught much. Yet I have not diminished the learning of my teachers by what I took from them any more than a dog lessens the sea by lapping it. The measure of a student is always too small against the measure of a master. That did not stop the students from keeping their distance, and the Rabbi grieved it openly. He folded his arms across his chest and cried, Woe to my two arms! They are like two scrolls of the Torah rolled up, their contents sealed.
Then he named one precious thing no one had thought to ask him. I expounded three hundred laws (some say three thousand) concerning the growing of Egyptian cucumbers, and not one person has ever asked me a single question about them, except Akiva ben Yosef. He turned to Rabbi Akiva and recalled the day they walked the road together. Akiva asked him how to plant the cucumbers. Rabbi Eliezer spoke a single word, and the entire field burst into cucumber vines. Akiva asked how to harvest them, and at another word all the cucumbers gathered themselves to one spot.
Still speaking, still teaching, Rabbi Eliezer fell back on his pillow and died. This passage from Sanhedrin 68a, preserved in Harris's 1901 Hebraic Literature, teaches the sorrow of unasked questions. Every master carries laws no one will ever think to ask about. When the master dies, those laws die with him. The only remedy is a disciple, like Akiva, who keeps asking.