Chapter 91:6
Non-Critical Illness on Shabbos
6. A person who is suffering from abdominal discomfort, may place a cup,
from which hot water was just poured (1) , on his stomach, even though it
still contains vapor (2). Similarly, one may warm up some clothing and
place them upon him (3).
FOOTNOTES:
(1) See HY 33:12 where the author rules that it is prohibited to place the
cup on one's stomach while it still contains hot water, due to the danger
of scalding.
(2) As we saw in HY 91:1, the Sages prohibited many forms of medical remedy
("refuah") on Shabbos, because if people saw someone being treated
medically, they might think that even grinding up the herbs to make the
medication is permitted on Shabbos. Grinding ("Tochen") is one of the 39
categories of prohibited creative activity on Shabbos ("Melachos").
According to the Rambam (Yad: Shabbos 21:31), even though it is clear that
the warm cup is being used as a remedy, since this kind of remedy could not
(at least in those days), be duplicated by taking drugs, it was not
included in the rabbinical prohibition against performing medical remedies
on Shabbos. It is important to note that if the person was not experiencing
discomfort, then placing the warm cup, and other similar remedies, would be
rabbinically prohibited because they involve exertion ("tircha") and are
considered weekday activities ("Uvda De'Chol") (Beis Yosef O'H 328).
According to some authorities, using an actual hot water bottle would be
prohibited, because it is clear that one is using it to relieve the
discomfort. However, the Mishna Berura (326:19) rules that if there is a
pressing need, one can rely on those who permit it,
(3) This is permitted even according to those who prohibit using a hot
water bottle, because it is not obvious that a remedy is being performed (
Mishna Berura 326:20).
