Rabbi Joshua ben Levi had a habit the other sages envied: the prophet Elijah came to him as a companion. The Exempla preserves the memory of one of their walks.
Elijah took Rabbi Joshua to the city walls and pointed upward — not to the gates as they stood in the second century, battered and charred by Roman siege, but to the gates as they would stand in the world to come. The future gates of Jerusalem, Elijah showed him, were not to be made of cedar or bronze or even gold. They would be hewn from single carbuncles — enormous gemstones, each a living ember of red light — polished into the shape of doorways.
The vision echoes the prophet Isaiah, who promised, "I will make your battlements of rubies, your gates of carbuncles, and your whole border of precious stones" (Isaiah 54:12). Jerusalem's rebuilt walls, the tradition teaches, will not glow because torches are lit on them; they will glow because they are themselves made of fire made solid.
The Exempla keeps this small story because it is a promise in the form of an image. No matter how often the earthly city is destroyed, Elijah has already shown a sage the gates of the coming Jerusalem — and those gates, once built, will not burn.
(From The Exempla of the Rabbis, Moses Gaster, 1924, no. 201, based on Bava Batra 75a.)