Guest post by Rabbi Michael J. Broyde*
The use of timers on Shabbat and Yom Tov involves two distinct halachic issues, one of which has been settled and one of which has not. The first is whether it is permitted to set a timer on Friday so that a prohibited action will take place on Shabbat. The second is whether it is permitted to adjust that timer on Shabbat to change when the action will occur.
A. Using Timers Set on Friday
The setting of a timer on Friday so that a prohibited act should occur automatically on Shabbat seems at first glance to be very similar to a well established halachic rule. Based on a talmudic discussion (Shabbat 17b-18a), Rambam (Shabbat 3:1) states:
It is permitted to start an action [melacha] on Friday even though that action is completed on Shabbat, since it is only forbidden to start work on Shabbat. However, when the work is done by itself on Shabbat, it is permitted to benefit from that work.
So too, Shulchan Aruch (Orach Chaim 252:1) states:
It is permitted to start an action on Friday near darkness even though the work cannot be completed on Friday and can only be finished on Shabbat.
Two exceptions to this rule were established. The Talmud (Shabbat 47b) states that one may not place a dish of water around a flame (which is emitting sparks) on Friday lest one shift the water on Shabbat and thus extinguish the flame.
More relevantly, the Talmud (Shabbat 18a) quotes in the name of Rava that it is prohibited to add wheat on Friday to a water mill that runs automatically on Shabbat since the mill produces a large amount of noise and this noise denigrates Shabbat (ziluta deShabbat). Furthermore, people will say that the owner of the mill is running it on Shabbat (Rama, Orach Chaim 252:5). Rav Yosef is quoted in the Talmud as disagreeing with Rava, and permitting any action done prior to Shabbat even if it creates large amounts of noise.
Rishonim disagree as to which opinion, Rava’s or Rav Yosef’s, is accepted as normative by halacha. Rabbenu Tam, Rambam and Rif all accept the opinion of Rav Yosef. On the other hand, Rabbenu Chananel, Rosh, Semag and Smak all appear to accept Rava’s approach. Rabbi Karo in the Shulchan Aruch states that it is permitted to place wheat in a self-grinding water mill on Friday (Orach Chaim 252:5). Rabbi Isserles (Rama), however, adds:
There are those authorities who prohibit placing wheat in the mill on Friday. We should worry about the prohibition of creating sound. This is the proper approach ab initio [lechatchila]. In cases of financial loss, it is permitted to be lenient.
Based on this stricture of the Rama, there are some who claim that using a timer on Shabbat should be prohibited when it creates audible or visible action. For example, absent some significant need, both Rabbi Moshe Feinstein and Rabbi Shlomo Zalman Auerbach agree that this rule prohibits one from playing a radio on Shabbat even if it is left on for all of Shabbat. Placing a radio on a timer is analogous to putting wheat into a water mill. Both cause noise on Shabbat and arouse suspicion that its owner has violated the laws of Shabbat. Hence, they rule that it is rabbinically prohibited to set a radio on a timer or to let it run the entire Shabbat.
Others have advanced different reasons to prohibit timers on Shabbat. Some claim that merely because the Talmud permitted the finishing of a prohibited action on Shabbat when it is started on Friday does not mean that a timer which does the entire action on Shabbat is permitted. Others have argued that just like it is forbidden to place a dish of water around a sparkling flame (see above) lest one adjust it, so too, it is prohibited to use a timer lest one set it on Shabbat. Finally, others argue that the only time it is permitted to start an action on Friday and finish on Shabbat is when no benefit is derived from the action on Shabbat. However, when a prohibited action is done for the sake of having the product on Shabbat, it is prohibited.
The consensus of the achronim as well as the accepted practice is not in harmony with any of the opinions which prohibit timers. As the Encyclopedia Talmudit (“Electricity” 18:679) states:
Many of the achronim permit one to set a Shabbat clock on Friday — and this is the common practice — even those who prohibit creating a sound permit the use of timers. . . since all know that these timers are set before Shabbat.
Essentially, since it has become common practice to use timers, there is no appearance of impropriety when timers are used. This approach has been accepted by most contemporary decisors such as Rabbi Waldenberg, Rabbi Breisch, Rabbi Henkin, Rabbi Auerbach, Rabbi Ovadia Yosef, the Chazon Ish, Maharam Schick and many others.
B. Adjusting Timers on Shabbat and Yom Tov
Before discussing whether a substantive prohibition exists to adjust a timer on Shabbat and Yom Tov, it is necessary to address a threshold question: are timers muktza. If timers are muktza, it is obviously prohibited to adjust them.
In a brief responsum Rabbi Moshe Feinstein asserts, without explanation, that one may not adjust a timer during Shabbat and Yom Tov because the timer is muktza. Other decisors have offered reasons for this assertion. Rabbi Benjamin Silber states that a timer is muktza “due to concern for monetary loss” (muktza machmat chisaron kis). Rabbi Auerbach and Rabbi Ovadia Yosef disagree and rule that timers are not muktza. They advance a number of reasons including the argument that the fact that the owner is presently using the timer makes it absurd to state that it is muktza due to a concern for monetary loss. This category of muktza is limited to items which are not regularly used and carefully stored due to concern that the item be damaged. However, one cannot reasonably assert that a timer is withheld from use as it is presently being used. This argument appears to be correct; it is difficult to grasp why a timer should be considered muktza if it is permitted to adjust it on Shabbat.
C. Grama: Indirect Causation
The Mishnah (Shabbat 120a) states that the biblical phrase “One may not do any work,” (Deuteronomy 12:4 and Exodus 20:10) only prohibits work directly caused by the person; however, work done indirectly — not caused by a human being, but by itself — is biblically permitted. As an example of indirect causation, the Mishnah states that it is permitted to place barrels of water in the path of a fire with the intent that the barrels catch fire, burst, and their content extinguish all the flames.
Most early authorities (rishonim) rule that even though indirectly caused actions are biblically permissible, they are rabbinically prohibited unless financial loss will be caused or a mitzvah will go unperformed. A minority of decisors accepts that biblically prohibited actions done indirectly are completely permissible on Shabbat. All authorities agree that on Yom Tov, indirect causation is permitted even absent special need.
The definition of “indirect” for the purposes of Shabbat, however, is in dispute. Three answers are given. The first answer posits that the critical distinction is the time delay. According to this definition, whenever there is a clear time delay between the action and the effect, this would be classified as indirect causation.
The second position states that the critical factor is whether the additional force needed to finish the action is present at the time of human activity. Only when the additional force is not present at the time of human activity is the action considered indirect.
A third view asserts that the critical factor is whether the indirect process used is the normal process. If the indirect process is the normal one, it is prohibited on Shabbat. Otherwise it is permitted.
Modern decisors resolve this three way dispute in different manners. Rabbi Shlomo Zalman Auerbach (Minchat Shlomo 110) states that since the halacha is unclear as to which definition of indirect causation is correct, one should avoid manipulating deliberately doing a grama which, if prohibited, would be a biblical violation. Minchat Ahava, a recent work by a modern Israeli decisor, seems to adopt only the second theory as normative. Finally, Rabbi Ovadia Yosef adopts the position that the first view is to be considered normative.
D. Adjusting Timers on Shabbat: Four Cases
Assuming that timers are not muktza, four distinct issues need to be addressed.
1) May one adjust the timer so that the appliance will start earlier than originally intended (e.g., move the dial so that a light scheduled to go on at midday goes on at 11 a.m.)?
This question is dependent on whether adjusting such a timer involves direct or indirect causation (grama) of the prohibited work. As explained above, a general rule is that actions done only through indirect causation are on a much lower level of prohibition on Shabbat; in many circumstances they are completely permitted. So too, as noted above, three basic answers are given. The first answer posits that the critical distinction is the time delay. The barrel case is permitted because the fire will not destroy the barrels until a considerable amount of time has elapsed, whereas the wind separates the wheat and chaff immediately. According to this definition, because there is a clear time delay between the action and the effect, this would be indirect causation. Since actions done via indirect causation are permitted on Shabbat in case of need or and in order to facilitate performance of a mitzvah, a timer set to go on at midday could be adjusted at 9 a.m. so that the appliance will go on at 10 a.m., if this were a case of need or mitzvah. On Yom Tov, indirect causation is permitted even absent special need and thus such adjustments are always permitted according to this reasoning. This is the view of Rabbi Ovadia Yosef and others.
The second position, that of Rabbi Joseph B. Soloveitchik and others, states that the critical factor is whether the additional force needed to finish the action is present at the time of human activity. Winnowing in the wind is prohibited only when the wind is blowing at the time the wheat is thrown into the wind; the barrel case is permitted since one is placing the barrels away from the fire. Placing the barrels actually in the fire would be prohibited. Since when adjusting a timer the additional force needed to finish the action, namely the rotation of the dial, is present at the time of human activity, all adjustments that hasten an action are prohibited. Thus, Rabbi Soloveitchik rules that under no circumstances may one adjust the timer so that an appliance will begin to operate earlier than expected.
A third view asserts that the critical factor is whether the indirect process used is the normal process. If the indirect process is the normal one, it is prohibited on Shabbat. Otherwise it is permitted. The barrel case is permitted only because it is not the normal manner to extinguish fire through a time delay. Winnowing, however, is frequently done through wind power. According to this approach, adjusting a timer is prohibited since it was designed to be used in this manner; however, placing ice cubes (or hot water) on a thermostat to increase the flow of heat (or cold air), would be permitted since that is an indirect and unusual manner of making the adjustment.
2) May one adjust the timer so that an appliance operates later than originally intended (e.g., move a dial on a timer so that a light set to go on at midday, now goes on at 2 p.m.)?
In this type of adjustment, no prohibited act occurs because one merely is maintaining the status quo of no work taking place. Thus nearly all authorities permit this type of adjustment. However, Rabbi Auerbach cautions that this permissive ruling does not apply to those timers where the timer is adjusted by removing and reinserting a peg. In those timers where the dial is rotated, adjustment to delay current flow should be permitted.
3) May one adjust the timer so that the electric current is extinguished earlier than expected (e.g., a light on a timer is set to go off at midday and one wants to move the dial so as to turn the light off at 10 a.m.)?
Adjusting a timer to extinguish an appliance prematurely involves the same considerations as adjusting the timer to extend the current flow. According to Rabbi Joseph B. Soloveitchik’s definition of indirect causation, such an action is forbidden. If one accepts time delay as the critical factor in determining whether an action is a result of direct or indirect action then in case of need or mitzvah one may adjust the timer to extinguish current flow earlier than expected.
One distinction, though, does exist between causing current to flow or be terminated. When the current flow turns on a light, a biblical violation occurs, whereas terminating a current flow involves at most a rabbinic violation. Rabbi Auerbach states that since the halacha is unclear as to which definition of indirect causation is correct, one should avoid manipulating a timer to hasten an action which, if prohibited, would be a biblical violation.
4) May one adjust the timer so that the electric current is extinguished later than expected (e.g., a light is set to go off at midday; may one move the dial so as to delay the turning off until 2 p.m.)?
Some authorities maintain that delaying the extinguishing of a light is forbidden, since it is analogous to adding fuel to a fire which is a violation of “burning” (“mavir“). Most authorities argue that this is incorrect, and this is analogous to shutting a window so as to prevent the wind from extinguishing a flame — one is only maintaining the status quo by removing an impediment to its continuation, as in situation (2) (moving a dial on a timer so that a light set to go on at midday, now goes on at 2 p.m.)
While initially a subject of some controversy, it has now become accepted that one may use a timer set on Friday to control all appliances.
The issue of adjusting timers on Shabbat has yet to be settled. Some authorities prohibit any adjustment of a timer on the grounds that it is muktza, and that is the view of Rabbi Feinstein.
Even if timers are not considered to be muktza, some authorities prohibit adjusting a timer to start or terminate current flow earlier than expected, and that is the view of Rabbi Soloveitchik.
Other authorities, accepting a different understanding of causation, permit this, and this is the view of both Rabbis Yosef and Auerbach who permits such adjustments in many situations.
Adjusting a timer to delay the onset of current flow appears not to violate any Shabbat or Yom Tov prohibition other than muktza according to most authorities.
* Rabbi Broyde is a law professor at Emory University, was the Founding Rabbi of the Young Israel in Atlanta, and is a dayan in the Beth Din of America. This short review is collected from a series of articles on electricity and halacha written many years ago, most of which were published in the Journal of Halacha and Contemporary Society, and three of which were co-authored with Rabbi Howard Jachter. See â€œUse of Elevators and Escalators on Sabbath and Holidays,â€ Journal of Halacha and Contemporary Society 29:60â€“89 (1995). [Co-authored with Rabbi Jachter.]; â€œThe Definition of Fire: A Theoretical Discourse with Some Practical Insights,â€ Distributed by Rabbinical Council of America (October 1993 â€œ×ž×©×ž×¢×•×ª ‘××©’ ×‘×”×œ×›×”: ‘×’×—×œ×ª ×©×œ ×ž×ª×›×ª’ ×•×—×•×˜ ×—×©×ž×œ×™ ×‘×™×•× ×˜×•×‘,â€ (=â€œIncandescent Light as Fire according to Jewish Lawâ€) Ohr Hamizrach 42(1):54â€“63 (Tishrei 5754 [= Fall 1993]); â€œElectrically Produced Fire or Light in Positive Commandments,â€ Journal of Halacha and Contemporary Society 25:89â€“127 (1993). [Co-author with Rabbi Jachter.]; â€œModern Technology and Sabbath Observance: Some Observations,â€ Journal of Halacha and Contemporary Society 23:63â€“100 (1992); and â€œThe Use of Electricity on Sabbath and Holidays According to Jewish Law,â€ Journal of Halacha and Contemporary Society 21:4â€“47 (1991) [Co-authored with Rabbi Jachter].  Rashi, Shabbat 18a.
 Tosafot Shabbat 18a; Rif on id.; Rambam quoted in Beit Yosef, Orach Chaim 324 “ein.”
 Rabbenu Channanel commenting on Shabbat 18a; Rosh on id.; see generally Beit Yosef commenting on Orach Chaim 252 and 324 for a complete list of authorities.
 Responsa Ben Yehudah 151; Goren David, Orach Chaim 15; Etan Aryeh 110-111.
 Iggerot Moshe, Orach Chaim 4:84. Rabbi Feinstein writes that the same prohibition applies to use of television on Shabbat.
 Minchat Shlomo pages 68-69 in the first edition. All references to Minchat Shlomo are to the first edition.
 This ruling is inapplicable to taping a television program on a video recorder on Shabbat (assuming the television is left off). In our opinion, that should be permitted because taping creates no visible sound or image on Shabbat and does not cause any disruption of Shabbat.
 In fact, some maintain (based on Nimukei Yosef, Bava Kama 22a) that a biblical prohibition is violated; see Responsa Ben Yehuda 151.
 Etan Aryeh #111; Mishpetei Uziel 1:223.
 For a discussion of this, see Magen Avraham commenting on Shulchan Aruch, Orach Chaim 307:3; Iggerot Moshe, Orach Chaim 4:60. Rabbi Feinstein writes that use of timers to automatically regulate machines to perform work forbidden to Jews on Shabbat is generally forbidden, with the exception of turning on and off lights. He believes that use of timers would severely disrupt the Shabbat atmosphere, since all of one’s work could be performed by machines. Rabbi Feinstein asserts that just as the Sages did not want, and therefore forbade our asking, non-Jews to perform work on our behalf on Shabbat for fear that this would disrupt the Shabbat atmosphere (see Rambam, Hilchot Shabbat 6:1) so too the Sages would not want machines to do work on our behalf during Shabbat. Rabbi Feinstein appears to be the lone authority to adopt this approach.
 See Tzitz Eliezer 1:20:9; Chelkat Yaakov 1:49; Edut Leyisrael p. 122; Minchat Shlomo p. 66; Yechave Daat 2:57; Chazon Ish, Orach Chaim 38:3 and 38:4; Maharam Shick, Orach Chaim 157; Minchat Moshe 8; Even Yekara 3:85; Yaskil Avdi, Orach Chaim 4:17.
 Iggerot Moshe, Yoreh Deah 3:47:4. He states that some adjustments are forbidden on a Biblical level and others are not, but he does not offer a rationale for these assertions.
 Az Nidberu 3:25 and 4:46:7. See Tzitz Eliezer 1:20:9, where Rabbi Waldenberg asserts that timers are muktza due to other considerations. Rabbi Breisch, Chelkat Yaakov 1:58 and 2:45, and Rabbi Weiss, Minchat Yitzchak 2:110, also consider timers to be muktza.
 Minchat Shlomo page 111.
 Yabia Omer 3:18:2
 Moreover, since timers (according to Rabbi Auerbach) only indirectly cause work to be done, they cannot be considered to be in the category of muktza known as “utensils of prohibited usage” (kli shemelachto leissur).
 If it is prohibited to use or adjust a timer, then such an appliance could be muktza. However, muktza cannot be the source of the prohibition and can only reflect a prohibition based on some other status.
 Biur Halacha, Orach Chaim 334:22 “degram kibui mutar” notes that the accepted opinion is that indirect causation is permitted in all categories of prohibited work, and not just extinguishing. For a general review of these issues, see Afikei Yam 4:2 and Har Tzvi, Orach Chaim 148. In Shabbat 120a the Mishna states that it is permitted to place barrels of water in the path of a fire with the intent that the barrels catch fire, burst, and their content extinguish the flames. The Talmud (Shabbat 120b) explains that this is an example of indirect causation which is permitted in cases of need. Elsewhere the Talmud (Bava Kama 60a) distinguishes between tort law and Shabbat rules, by stating that for the purposes of Shabbat rules one is responsible for indirectly caused activity (but in tort one is not). The example the Talmud gives is one who is winnowing (separating wheat and chaff) on Shabbat violates the biblical prohibition by throwing the wheat into the air and letting the wind separate the wheat and chaff. This is prohibited even though done indirectly and requires the presence of an additional force (the wind) to complete the action. The question that emerges is why is the barrel case permitted and the winnowing case forbidden?
 See Tosafot, Beitza 22a; Mamar Mordechai, Orach Chaim 514:10; Rashba, Avodat Hakodesh, Shaar 3:3; Ran, Shabbat 120b; Meiri, Shabbat 120b; Rama, Shulchan Aruch, Orach Chaim 334:22; Maharam Shick 157; Yabia Omer 1 Orach Chaim 21:14; Chazon Ish, Orach Chaim 38:2.
 See sources cited above in note 18.
 See e.g. comments of Magen Avraham on Orach Chaim 514:3 explaining Rosh, Beitza 22a; Comments of Korban Netanel, Beitza 22b. Mishnah Berurah, Biur Halacha, Orach Chaim 334:22 “degram kibui mutar” notes that the accepted opinion is that indirect causation is permitted in all categories of prohibited work in a case of need, and not just extinguishing.
 Shulchan Aruch, Orach Chaim 334:22 (and Biur Halacha).
 Ketav Sofer, Orach Chaim 55; Zera Emet, Orach Chaim 44. See also, Maharam Shick, Orach Chaim 157; Chazon Ish, Orach Chaim 38:2; Chelkat Yakov 1:49.
 See e.g., Rabbi Hershel Schachter, Maaseh Ugrama Behalacha, Beit Yosef Shaul 1 70-72 (1985). Rabbi Schachter cites both earlier and later authorities who agree with this approach. For another review of this topic, with the same conclusion, see Responsa Tefila LeMoshe 2 23:3-4.
 Even Haozer, Orach Chaim 328; Meorei Esh pp. 201-202. See Achiezer 3:60 for a further explanation of this position.
 Shmirat Shabbat Kehilchatah 13:25 n. 94 appears to adopt a slightly different rule.
 Minchat Ahava 1 1:14.
 Yabia Omer 3:18.
 Shulchan Aruch, Orach Chaim 334:22 (and Biur Halacha).
 Yabia Omer 3:18; Ketav Sofer, Orach Chaim 55; Zera Emet, Orach Chaim 44. See also, Maharam Shick, Orach Chaim 157; Chazon Ish, Orach Chaim 38:2; Chelkat Yakov 1:49.
 Rabbi Soloveitchik’s position is fully explained in an article by Rabbi Hershel Schachter, Maaseh Ugrama Behalacha, Beit Yosef Shaul 1 70-72 (1985). Rabbi Schachter cites both earlier and later authorities who agree with this approach.
 Even Haozer, Orach Chaim 328; Meorei Esh pp. 201-202. See Achiezer 3:60 for a further explanation of this position.
 Minchat Shlomo p.111. Rabbi Feinstein (Iggerot Moshe, Orach Chaim 4:60) writes that a Sabbath violation is caused by delaying the onset of current, but he does not explain the reason for his position. See Az Nidberu 8:32 where Rabbi Silber argues that any adjustment of a timer is a violation of building (boneh). It is possible that the Chazon Ish felt that way also; see Chazon Ish, Orach Chaim 38:2.
 Minchat Shlomo page 111. Only removing the peg is permitted, since that delays the onset of the electrical flow. Reinserting the peg to turn the current off at the time desired is only permitted if one accepts those authorities discussed above that one can hasten the extinguishing of an appliance.
 Shmirat Shabbat Kehilchatah 13:25 n. 94 cites Rabbi Auerbach as maintaining that one may also delay the onset of current in those timers whose adjustment involves the pressing of a button to allow movement of the dial and releasing this button to set the dial.
 Minchat Shlomo page 110.
 Yaskil Avdi, Orach Chaim 7:23 and Az Nidberu 8:32.
 Minchat Shlomo, p. 111; Yabia Omer 3:18.