The Rebbe was always right ...
According to food historians, chicken soup was already being prescribed as a cure for the common cold in Ancient Egypt. The 10th century Persian physician Avicenna also referred to the curative powers of chicken soup in his writings. In the 12th century the Jewish sage Maimonides wrote that chicken soup "has virtue in rectifying corrupted humours", and recommended it as nutrition for convalescents; Maimonides also particularly recommended chicken soup for people suffering from hemorrhoids and the early stages of leprosy.
Chicken soup: simple to prepare, relatively cheap, nutritious, and easy on the digestive system, chicken soup is a good food for winter convalescents. Probably more significant, sipping warm soup can clear nasal passages, serving as a natural decongestant, which also relieves cold and flu symptoms. Last but not least, chicken soup can be beneficial due to the placebo effect of comfort foods.
The soup is often associated with European Jewish cuisine, in which chicken soup is the basis for several traditional holiday courses, such as chicken soup with matzah balls for Passover. Although poverty was rampant in the shtetl, chicken-raising required little land or financial investment. Every Jewish family would try to acquire at least one chicken in honor of the Shabbat meals, and would try to stretch it as far as it would go. Thus, every part of the chicken was used, leading to the creation of such dishes as p'tcha (chicken feet), pupiks (roasted gizzards), chopped liver (chicken liver), stuffed hezel (chicken neck), and schmaltz and greben (respectively, chicken fat and cracklings made from the fat and the skins). Chicken soup also proved to be a "recyclable" dish. Parts of the chicken—especially the breasts, which produce a more delicate flavor during the boiling process—were boiled as chicken soup and then reused afterwards in such dishes as kreplach, knishes, and blintzes. Tortelloni-like kreplach are traditionally added to the soup on the eve of Yom Kippur. Lokshen (flat egg noodles) are also a favorite Jewish addition to chicken soup. A lesser known garnish is unlaid chicken eggs, removed from the ovaries of a laying chicken. Herbs traditionally served with Jewish chicken soup are parsley and dill.