Treating stomach pains with a vessel of hot water
A large amount of water: One who has a stomach pains is forbidden to place on his stomach a vessel that has hot water
The reason for this is: because he may come to spill it on majority of his body and it will thus be considered as if he has washed majority of his body in hot water.
A small amount: [Furthermore] even if there is only a small amount of hot water [in the vessel] which is not enough to wash majority of one’s body [if it were to spill], nevertheless if it were heated on Shabbos even a little, [even if this were] to the point that it is not [yet] Yad Soledes, it is forbidden [to place in a vessel on one’s body for the reason] explained [in the previous Halacha, that one may not bathe even minority of one’s body in water heated on Shabbos].
On a weekday: [Furthermore] even on a weekday this is not allowed to be done because of the possible danger [that it involves] as at times the water is very hot [and may come to spill on one’s body and give him a serious burn].
Placing hot clothing on it: However it is permitted to heat up clothing and place them on ones stomach even on Shabbos.
It is forbidden to place an [open] vessel of hot water on ones stomach even during the week due to fear that it may spill and cause a burn. On Shabbos this is forbidden also due to the bathing prohibition, unless it were heated before Shabbos and is not wet enough to wet majority of one’s body if it were to spill. [However, nevertheless it would remain forbidden due to danger.]
If the water is placed in a closed bottle may one place it on his stomach?
Yes, as there is now no suspicion that it will spill. [As well there is no medication prohibition involved here as is seen from the fact that Admur makes no mention of it.]