For thirteen years, Rabbi Shimon bar Yohai and his son Rabbi Elazar hid in a cave, fugitives from the Roman Empire. The Talmud (Shabbat 33b) records how they survived and what happened when they emerged.
A carob tree grew at the cave's entrance, and a spring of water appeared — miraculous sustenance for the duration of their exile. They buried themselves in sand up to their necks to preserve their clothing, and spent every hour of every day studying Torah. For thirteen years, nothing existed for them but Torah, prayer, and survival.
When they finally emerged — after hearing that the emperor had died and the decree against them was lifted — they saw people plowing fields and planting seeds. Rabbi Shimon was enraged. "These people abandon eternal life and busy themselves with temporal life!" Everywhere he looked, his gaze set things on fire.
A heavenly voice spoke: "Did you emerge to destroy My world? Go back to your cave!" They returned for another twelve months. When they came out again, Rabbi Elazar still destroyed whatever he saw — but Rabbi Shimon healed it. "My son, you and I are sufficient for the world," he said.
On the eve of the Sabbath, they saw an old man running with two bundles of myrtle. "What are these for?" they asked. "To honor the Sabbath," he replied. Rabbi Shimon turned to his son: "See how precious the commandments are to Israel." And their minds were finally set at ease. The world was not as hollow as the cave had made it seem.