Question: Is one permitted to boil water in an electric hot water urn on Shabbos if the urn is controlled by a Shabbos clock?
Answer: While some authorities say yes (in certain circumstances), the gaon Rabbi Moshe Feinstein (Responsa Igrot Moshe 4:60) ruled that it’s prohibited.
To understand this very complex issue, it’s important to review some of the relevant verses in the Torah relating to the prohibition of working on Shabbat.
The Ten Commandments (Exodus 20:10) states: “Veyom ha’shevi’i shabbatla’Shem Elokecha lo ta’aseh kol melacha ata u’vincha u’vitecha avdecha va’amat’cha u’vehemtecha ve’gercha asher bi’she’arecha – But the seventh day is a Sabbath to Hashem, your G-d; you shall not do any labor – you, your son, your daughter, your male servant, your maidservant, your cattle, and your convert within your gates.”
Rashi (ad loc.), citing the Gemara (Shabbos 121a), explains that “your son, your daughter” refers to minor children. One is liable for shevitat ketanim, one’s minor children resting on Shabbat. (Adult children are commanded to rest by dint of the word “you” in this verse.)
This verse contains much pertinent information relevant to our discussion. First, the words “you shall not do any labor” limit the prohibition to direct action, not indirect action, called gerama (Shabbos 120a), or activities that happen on their own (Jerusalem Talmud, Shabbos 2:1). Second, the prohibition of muktzeh comes from here (Pesachim 16b).
In Parshat Mishpatim (Exodus 23:12), the Torah says, “Sheshet yamim ta’aseh ma’asecha u’vayom hashevi’i tishbot lema’an yanuach shor’cha va’chamorecha ve’yinafesh ben amat’cha ve’hager – Six days shall you accomplish your activities [labors] and on the seventh day you shall rest, so that your ox and your donkey may rest and your maidservant’s son and sojourner may be refreshed.”
Rashi (ad loc.) explains that “the rest” of your ox and your donkey involves them being allowed to graze freely since restraining them in the house would not be considered pleasurable rest, but pain.
The Gemara (Shabbos 18a) discusses activities one may commence on the eve of Shabbat even though they will continue on their own on Shabbat. These include opening a source of water to hydrate a garden, placing fragrant incense under clothing, and placing sulfur under silver vessels (done, says Rashi, to blacken the silver in order to accentuate engraved images such as flowers on them). One may not, however, put wheat grains into a watermill unless there is enough time for them to be ground before Shabbat.
The Gemara wonders why the latter activity is prohibited while the others are not. Rabbah says mill activity is forbidden because it makes noise (see Rema, Orach Chayim 252:5). R. Yosef dissents, saying to Rabbah, “Why does my master not say that the reason is shevitat kelim – keeping one’s utensils from [performing] labor on Shabbat – as we learned in a baraita? We expound Exodus 23:13, ‘U’vechol asher amarti aleichem tishameru – And all that I have said to you shall you watch [i.e., keep].’ This includes shevitat kelim.”
Our Gemara concludes, though, that only Beit Shammai – not Beit Hillel – rule there is a problem of shevitat kelim.
If so, we can readily understand leniencies regarding the use, on Shabbat, of various appliances such as refrigerators, whose use on Shabbat no one questions since they keep our food from spoiling. Lights are also tools we continue to use on Shabbat since they were already operating before Shabbat. Nothing new needs to be done in the course of Shabbat to cause these utensils to work for us.
As for boiling water by means of an electric timer – i.e., a Shabbos clock – that’s set before Shabbat: It would seem that one has not initiated any action on Shabbat. Furthermore, it’s relevant that hot water is undoubtedly considered vital for infants and the elderly.
(To be continued)