The Sages prohibited taking medicines on Shabbat – unless the individual is suffering from a condition that might be life-threatening – due to the concern that the medicine may be prepared by grinding herbs in a forbidden manner. If, however, the medicinal product is one that is enjoyed by healthy people, as well, then there is no prohibition.
One may not soak asafoetida in lukewarm water to prepare a medicinal drink from it; however, one may place it into vinegar like a standard spice.
The Gemara asks: For what purpose is soaked asafoetida prepared?
The Gemara answers: As a cure for heaviness of the heart. One who feels a pain in his heart drinks asafoetida. The Gemara relates: Rav Aḥa bar Yosef felt heaviness in his heart. He came before Mar Ukva to ask his advice. Mar Ukva said to him: Go drink the weight of three shekels of asafoetida in three days. He went and drank on Thursday and Shabbat eve. In the morning, he went and asked in the study hall if he could drink it on Shabbat. They said to him:
The Sage from the school of Rav Adda taught, and others say, that the Sage from the school of Mar bar Rav Adda taught: A person may drink asafoetida on Shabbat, even a kav or two kav, and he need not be concerned about the decree prohibiting medicine, because asafoetida is drunk by healthy people as well.
Ferula assafoetida, also known as devil’s dung or giant fennel, is a perennial plant of the umbel family. It has a thick root and a stem with leafed branches. The asafoetida grows to a height of 6-9 feet. It is native mainly to Afghanistan and the neighboring regions. The plant grows for several years until it blossoms and produces fruit, after which it dies. Medicinal asafoetida is manufactured from the resin found in the root of the plant. It was used, and is still used today, as a medicine in the form of powder, creams, pills, etc., both for intestinal diseases and for strengthening the nervous system. In certain places, asafoetida is even used as a spice. Consumption of asafetida in amounts of more than a gram is dangerous and can lead to poisoning.