RAV KOOK ON VaYishlach Part 1: Reliance on Miracles

Miracles were no novelty for Rabbi Zeira. The Talmud in Baba Metzia 85a elates that the third-century scholar fasted for a hundred days in order to protect himself from the fires of hell. But Rabbi Zeira was not content with theoretical preparations. Once a month he would test himself by itting down in a burning furnace, to see if he would feel the heat. He didn't. (Once his clothes were singed, but that story is for another time.) Yet, on very windy days, Rabbi Zeira was careful not to walk among the palm-trees, lest a strong wind should knock a tree over. His caution in orchards seems bizarre. Why should a man who can sit unharmed in a burning furnace be concerned about the possibility of a falling tree?