The Previous Rebbe writes: "My grandmother, Rebbetzin Rivkah, once developed a lung ailment. The doctor of the city of Vitebsk 'wrote her off' [as being incurable]. She then went to her father-in-law, the Tzemach Tzedek, and he interpreted the Talmudic expression 'From here we deduce that permission is given to the practitioner to heal.' The Rebbe explained, 'The practitioner is only given permission from on High to heal, but as for any other advice, he has no say.'"

Sefer HaSichos 5705, p. 8