PREPARATION OF FOOD
The seriously ill patient.
94. It is permissible to cook on the Sabbath for a seriously ill patient who needs hot food or drink in order to fortify him when such is not already available. This is true even if a neighbor has hot food and drink but is asleep, or has not enough for himself.
95. One must only cook the amount necessary for the patient. More food than necessary for the patient may not be added, even to the same pot and even if this was done before the pot is put on the fire or the fire lit. However if time is of the essence one does not need to be exact. Similarly if only a large pot is available, and would spoil if only the small amount required for the patient is cooked, one may cook as much as necessary to avoid this, thus ensuring that hot food be available for the patient.
96. When cooking for a seriously ill patient, one should preferably use an electric rather than a gas stove, since with the latter a match or other lighter has first to be lit, whereas with the former there is only one act of lighting. If however the gas stove already has a pilot light burning and turning the gas on automatically results in it being lit, there is no difference between the two stoves. If a micro-wave oven is available it is to be preferred since no Torah precept is set aside.
97. The gas or electricity may not be extinguished or decreased after the food or drink has been cooked.
98. No one may partake of the left-over food or drink that has been cooked on the Sabbath for a seriously ill patient. Even a non-seriously ill patient may not do so unless he has no food or drink and a non-Jew is not available to cook for him (see paragraph 100 below). The cook may taste of the food to make sure that it is tasty. Once the Sabbath is over, even a healthy person may eat the left-over food, and the pot in which the food was cooked remains in its previous "kosher" status (see paragraph 100 below). If however the Sunday was a Festival, a healthy person may not eat the left-over food, although water that was boiled on the Sabbath and then allowed to cool may be drunk on the Festival.
99. If the patient became ill, and seriously so, on the Sabbath, and the food in its original state was not edible uncooked, for example meat, fish or potatoes, then it is muktzeh and may not be moved even after cooking, except for the patient. However the leftovers may be disposed of or put into the refrigerator if leaving them exposed would attract flies, etc. If, however, the patient was already ill before the Sabbath commenced, the food may be moved even if not for the patient.
The non-seriously ill patient.
100. A non-Jew may be asked to cook or heat food or drink for a non-seriously ill patient. However a Jew must not take part as he would normally do on a week-day; even putting the food in the pot before it is placed on the flame is forbidden. It is similarly forbidden to cover the pot unless it is fully cooked, nor may the food be stirred. A healthy person may not partake of the food or drink on the Sabbath. Competent Rabbinic authority should be consulted after the Sabbath as to whether the food may be eaten then (even by the patient himself), and also regarding the Halachic status of the vessels in which the food was cooked.
 Shemirat Shabbat Kehilchata 32:72.
 Shemirat Shabbat Kehilchata 32:74 in the name of R. Sh.Z. Auerbach. See ibid. note 189.
 Shemirat Shabbat Kehilchata 32:75.
 Shemirat Shabbat Kehilchata 32:76.
 Oral communication from R. Sh.Z. Auerbach. See Resp. Iggerot Moshe Orach Chayyim 3:52.
 Shemirat Shabbat Kehilchata 32:77.
 Shemirat Shabbat Kehilchata 32:77, note 200.
 Shemirat Shabbat Kehilchata 32:78.
 Shemirat Shabbat Kehilchata 32:77, note 202.
 Shemirat Shabbat Kehilchata 32:79.
 A non-Jew's cooking is permitted for a sick person.
 Shemirat Shabbat Kehilchata 38:11.