Rabbi Yochanan, in expounding Isa. liv. 12, said, "The Holy One — blessed be He! — will bring precious stones and pearls, each measuring thirty cubits by thirty, and polishing them down to twenty cubits by ten, will place them in the gates of Jerusalem. A certain disciple contemptuously observed, " No one has ever yet seen a precious stone as large as a small bird's egg, and is it likely that such immense ones as these have any existence? He happened one day after this to go forth on a voyage, and there in the sea he saw the angels quarrying precious stones and pearls like those his Rabbi had told him of, and upon inquiry he learned that they were intended for the gates of Jerusalem. On his return he went straight to Rabbi Yochanan and told him what he had seen and heard.