Ibn Majah narrated in his Sunan (collection of Hadith) that Anas bin Malik said, I heard the Messenger of Allah saying:
Sciatica is an ailment that starts from the hip joint, then descends to the thigh from the backside of the body. Sometimes, sciatica reaches the ankles and the longer the ailment remains, the lower it descends and the weaker the legs and thighs become. There are two beneficial understandings in the Hadith mentioned, medical and linguistic. Linguistically, the Hadith proves that we are allowed to call this ailment an ‘Irq (nerve) Nasa (sciatic nerve), on the contrary to the opinion of some people. They said that the Noso is the nerve itself and thus the two words together are redundant. Answering this claim takes two forms. First, the word ‘Irq (nerve) is more general than the word Noso (sciatic nerve). Hence the term ‘Iraq An-Nasa’ gives the general and the specific meanings desired. Second, the Nasa is an ailment that attacks the nerve, and thus the word Nasa should be included in the name given to the ailment [as it specifies the area where the nerve is causing pain]. It was reported that the name ‘Irq Nasa’ is called as such because it makes the people forget (Nasa) any other pain.
The sciatic nerve starts from the hips until the bottom of the foot from behind the ankles. In addition, the nomad’s ewe has several qualities, such as being small in size, producing lesser excrements, and having a soft essence. The nomad’s ewe In addition grazes on beneficial wild plants, such as wormwood and lavender cotton, and so forth. When the ewe feeds on these wild plants, they will mix with and soften the ewe’s flesh, especially the fatty tail. Although the ewe’s milk carries in it the effective ingredients of the wild plants, the tail has two qualities that the milk does not have, being a laxative and leading the septic substances to maturity [making them ready to be extracted from the body].