Rabbi Yochanan ben Zakkai, the sage who rescued Torah study from the ashes of Jerusalem's destruction in 70 CE by founding the academy at Yavneh, once taught that in the future, when Jerusalem is rebuilt, the eastern gate and its two posts will be fashioned from a single pearl, an enormous luminous stone, thirty cubits by thirty cubits.
A min, a sectarian scoffer, overheard him and laughed. We barely have pearls the size of a dove's egg, he said. Who would believe in a gate made of one? The scoffer walked away shaking his head at the credulity of rabbis.
Some time later, this same man was sailing on a merchant vessel when the ship passed over a quiet patch of sea and something enormous shimmered beneath the surface. He leaned over the rail. In the water, he saw the mal'achei hasharet, the ministering angels, quietly at work, sawing and shaping the very pearl the Rabbi had described. The scoffer understood in a single breath that the olam haba, the world to come, had raw materials already being prepared below the waves.
He hurried back to the Land of Israel as soon as he docked and went straight to Rabbi Yochanan. You were right, he said. I saw them at work in the deep. And then, because he could not resist the impulse of a reformed mocker, he added, Had I not seen it with my own eyes, I would still laugh. Rabbi Yochanan looked at him steadily. Under his gaze, the man who had scorned the teaching turned into a heap of bones on the spot.
This exemplum, preserved as number 203 in Moses Gaster's 1924 Exempla of the Rabbis and told in Bava Batra 75a, is jarring, but it makes an ancient point. It is one thing to doubt a teaching before you have seen the evidence. It is another thing to have the evidence, walk it back to the Rabbi, and still brag about your old doubt. The pearl was real, the angels were real, and the man's laughter had become an insult heaven did not forget.