801. Washing with Foul Water

Shabbos 21:28

One may apply oil and massage the abdomen on Shabbos so long as he does both things simultaneously, to avoid following the normal weekday procedure. One may not exercise on Shabbos, such as having others walk on him until he gets exerted and starts to perspire, or walking until one exerts himself and starts to perspire. One may likewise not exert himself on Shabbos until he perspires because this is a form of healing. Similarly, one may not stand in the mud baths of Israel as this exerts a person and is used as a healing practice.

Shabbos 21:29

One may not wash in water that loosens the bowels; in quicksand; in water used to soak flax, which causes it to develop a foul odor; in the Dead Sea; in foul water from the Mediterranean. All of these cause a person discomfort, which is counter to the idea that “you shall call Shabbos a delight” (Isaiah 58:13). If a person does not remain in one of these bodies of water for a long time, emerging immediately instead, then it is permitted even for a person who has sores on his scalp.