According to Chassidic tradition, when Rav Zaddok first arrived in lzhbitza, he stood silently in the back of the study hall during the Rebbe's Friday night and Shabbos morning "tischen." The Chassidim sought in vain to detect on the face of the Lithuanian genius some sign of his being moved by the teachings of Rav Mordechai Yoseph. Late Shabbos afternoon, as darkness descended upon the shtetl, the Rebbe quietly addressed his followers. Suddenly from the back of the beis medrash, a man began to scream "The Rebbe is burning me! The Rebbe is throwing acid upon my heart!"
Drawing of the Izhbitzer Rebbe