Forty years before the destruction of the Second Temple, he observed fasts in order that Jerusalem might not be destroyed, and would eat only at night, and when the Romans encircled Jerusalem in order to destroy it, Johanan ben Zakai had only three requests from Vespasian, and one of them was to give him medicine measures to heal Rabbi Zadok. The Mishnah in tractate Gittin elaborates on the ways Rabbi Zadok was healed.