Tamid 28b: A Tree in the Shul Courtyard

Tamid 28b: Rabbi Eliezer ben Yaakov says: From where do we derive the law that we may not build a wooden portico in the courtyard of the Beis Hamikdash? Because the Torah says, “Do not plant an asheirah, any wood next to the mizbeyach of Hashem your G-d” (Devarim 16:21).

Sifri, Shoftim: From where do we derive the law that we may not plant a tree or build a house on the Temple Mount? Because the Torah says, “Any wood next to the mizbeyach of Hashem your G-d.” Rabbi Eliezer [ben Yaakov] says: From where do we derive the law that we may not build a wooden portico in the courtyard of the Beis Hamikdash? Because the Torah says, “Next to the mizbeyach of Hashem your G-d.”

The Rambam (Avodah Zarah 6:9) rules in accordance with the first opinion in the Sifri that one may not plant a tree, but adopts Rabbi Eliezer ben Yaakov’s condition that it is only forbidden in the courtyard, not the entire Temple Mount.

Rabbi Akiva Eiger Orach Chaim 150:1:  Planting a tree next to a shul is Rabbinically forbidden.

תמיד כח ע”ב: תניא ר’ אליעזר בן יעקב אומר מנין שאין עושין אכסדראות בעזרה ת”ל לא תטע לך אשרה כל עץ אצל מזבח ה׳ אלהיך, הכי קאמר: לא תטע לך אשרה, לא תטע לך כל עץ אצל מזבח ה׳ א-להיךִ.

ספרי שופטים: ומנין לנוטע אילן ובונה בית בהר הבית שהוא עובר בלא תעשה ת״ל כל עץ אצל מזבח ה׳ אלהיך. ר׳ אליעזר אומר מנין שאין עושים אכסדרה בעזרה ת״ל אצל מזבח ה׳ א-להיך.

רמב”ם הלכות עבודה זרה ו,ט:  הנוטע אילן אצל המזבח או בכל העזרה, בין אילן סרק ובין אילן מאכל, אע”פ שעשאו לנוי למקדש ויופי לו – הרי זה לוקה, שנאמר: “לא תטע לך אשרה כל עץ אצל מזבח ה’ אלקיך”, מפני שהיה זה דרך העכו”ם נוטעין אילנות בצד מזבח שלהם כדי שיתקבצו שם העם.

ר’ עקיבא איגר או”ח קנ,א: וכתב ר’ דוד עראמה בפירוש להרמב”ם, דאפילו אצל בית הכנסת אסור מדרבנן.

Once, someone decided to plant trees in the courtyard of the main shul of Bnei Brak. The Chazon Ish, basing himself on Rabbi Akiva Eiger, was against the idea. But he did not wish to impose his view on others, so he came up with a clever trick: he sent people to each of the major rabbis in Bnei Brak, telling each one that Rabbi So-and-so had permitted the planting of the trees. This, he reasoned, would motivate them to forbid it, since it is human nature for a rabbi to want to show everyone that he has a mind of his own and does not just go along with what everyone else says. Thus all the rabbis would forbid it.

In the end, however, the trick failed and all the rabbis permitted planting the trees. 

Source: Divrei Siach, Vayechi 5781


Peah 4,2: Opening the Window in the Winter

Peah 4:2: Peah must be left for the poor while still connected to the ground; the owner of the field is not allowed to harvest it and distribute it to the poor. Even if 99 poor people want to have it distributed to them, and one wants to cut it from the ground himself, we listen to the one, since he is saying in accordance with the halacha.

פאה פרק ד’ משנה א-ב’: הפאה נתנת במחובר לקרקע…אפילו תשעים ותשעה אומרים לחלק ואחד אומר לבוז. לזה שומעין. שאמר כהלכה.

R’ Chaim Kanievsky in Shaarei Emunah on this Mishnah writes: “We have heard in the name of Rabbi Yisroel Salanter zt”l that if there are many people in a room and some want to open the window and others want it closed, he ruled that in the summer those who want it open win, even if it is one against a hundred; and in the winter it is the opposite. He brings proof from this Mishnah, but it seems there is no proof, because here it is a Torah law, derived from pesukim, that one must leave the peah connected to the ground, whereas there is it only a question of what is usually done, so if there is a reason to deviate from the usual, it would seem that we follow whatever the majority of the people want.”

In the winter of 2020, when many arguments developed in the shuls between cold, shivering people and people worried about catching the coronavirus, Rabbi Yitzchok Zilberstein followed Reb Yisroel Salanter’s opinion but with a twist to reflect the current situation: he ruled that the ones wanting the window open always win, even if they are the minority. “Let anyone who is cold buy a heater,” he said.


Bechoros 24b: Using a Sefer to Push Other Seforim Aside

Bechoros 24b: Rabbi Yossi ben Hameshulam says: When slaughtering a bechor offering, one should push aside the hair with the knife to uncover the place of shechitah, and one is even allowed to pull out the hair (and it is not forbidden under the prohibition of shearing a bechor). Rabbi Asi said in the name of Resh Lakish: It is only permitted to pull out the hair by hand. But it says with the knife! – Change the words of the Mishnah from “with the knife” to “for the knife”.

רבי יוסי בן המשולם אומר: השוחט את הבכור ־ עושה מקום בקופיץ מיכן ומיכן ותולש את השער. אמר רב אסי אמר ריש לקיש: לא שנו אלא ביד, אבל בכלי אסור. והקתני: עושה מקום בקופיץ מיכן ומיכןִ! תני: לקופיץ.

Someone once asked R’ Chaim Kanievsky, “When I go to put a sefer away on the shelf, and the other seforim are packed closely together, am I allowed to use the sefer in my hand to push the others to the side and make room, or is that a disgrace to the sefer?”

To the questioner’s surprise, R’ Chaim replied, “It is an explicit Mishnah in Bechoros that one may do this. It says that one may use the knife, which is a holy vessel of the Beis Hamikdash, to push aside the hair of a korban. Although the Gemara modifies the text, that is only because pulling out hair using the knife would be forbidden. But using the knife to push aside the hair is permitted. So we see that this is called using a holy object for a holy purpose, since it is a preparation for the avodah. Here too, pushing aside the other seforim is a preparation for putting the sefer back and is permitted.”

He added, “One could ask a similar question about using one’s tefillin to push his shirt sleeve up to make room for the tefillin. And the answer is that it is permitted, as we said.”

Source: Divrei Siach, Vayechi 5781

Moed Katan

Moed Katan 15b: Bathing during Shloshim

Moed Katan 15b: A mourner is forbidden to bathe, as it says, “Do not anoint with oil” (Shmuel II 14:2) – and bathing is included in anointing.

Yoreh Deah 381:1. Rema: By law, this is only forbidden during shiva, but the custom today is to forbid bathing for the whole shloshim. And we should not change this custom, since it is an old custom, established by great rabbis.

מועד קטן טו ע”ב: אבל אסור ברחיצה, דכתיב (שמואל ב׳ י״ד) ואל תסוכי שמן, ורחיצה בכלל סיכה.

יו”ד סימן שפא,א: רחיצה כיצד, אסור לרחוץ כל גופו אפילו בצונן, אבל פניו ידיו ורגליו בחמין אסור בצונן מותר, ואם היה מלוכלך בטיט וצואה רוחץ כדרכו ואינו חושש: הגה וכל זה מדינא אינו אסור רק שבעה אבל אח״כ מותר ברחיצה אלא שנהגו האידנא לאסור כל רחיצה כל ל׳ יום ואפי׳ לחוף הראש אסור ואין לשנות המנהג כי מנהג קדום הוא ונתייסד על פי ותיקין.

One day in 1876, a guest was sitting with R’ Yitzchok Elchonon Spector, when a man came in and asked, “Rabbi, I am a mourner. Am I permitted to go to the bathhouse?” Without hesitation, he answered him, “You are permitted.”

The questioner was not satisfied with this instant response, and spoke again: “Rabbi, I am in mourning for my father.” “Permitted, you are permitted,” the rav answered, using a double expression.

But this still did not settle the mind of the questioner, who asked a third time, “Only to sweat, or even to wash in hot water?” The rav answered him with a friendly smile, but also with surprise: “I just told you that you are permitted, and I said it without adding any details or qualifications. If so, go without delay, before I change my mind!”

After the man left, the rav looked at the guest, noticing his amazement, and guessing his thoughts. How and why could he rule leniently, contrary to the ruling of the Rema, who cites an enactment of the early rabbis? He said jokingly, “My guest will go on his way and tell people that the head of the Beis Din of Kovno gives hasty, mistaken rulings.” The guest also responded in jest, “Certainly I will.”

“If so,” said the rav, “let me ask you: do you know the Maharshal’s reason for forbidding bathing?” The guest answered: “Because of the prohibition against having a haircut; for the usual way is to have a haircut in the bathhouse.” “In that case,” continued R’ Yitzchok Elchonon, “why are we allowed to bathe during Chol Hamoed? That is also a period when we are forbidden to have a haircut! I know that this is the problem posed by the Taz on Yoreh Deah 381:1, and he answers that since everyone is forbidden to have a haircut then, we do not worry that one might forget.” He smiled, “Here too, today is one of the days of Sefiras Haomer, when the custom is to forbid haircuts. So why would this man forget and get a haircut? Therefore, he is allowed to bathe.

“I urged the questioner to go immediately, because it looked like he wanted to argue against my ruling. He wanted to object that the prohibition on haircuts during Chol Hamoed is a real Rabbinic prohibition, while during Sefirah it is only a minhag. I did not want to enter into a detailed discussion with him, so I did not point out to him that the prohibition against bathing in hot water after shivah is also only a minhag.”

Source: Mourning in Halacha, p. 211

[His last point is that the questioner could have objected that perhaps people will take the minhag of Sefirah lightly and get haircuts in the bathhouse during Sefirah. R’ Yitzchok Elchonon’s response is that the minhag not to bathe during shloshim was not set up for such people who take minhagim lightly, because then why would they respect this minhag in the first place? Rather the “minhag vasikin” brought by the Rema was aimed at carefully observant Jews, and such people would never come to take a haircut in Sefirah.]

Bava Metzia

Bava Metzia 110b: Using a Hiring Manager to Avoid Bal Tolin

Bava Metzia 110b: If one appointed an agent to hire workers, neither he nor the agent transgresses “bal tolin” (the prohibition to delay a worker’s wages overnight). He does not transgress because he did not hire them, and the agent does not transgress because he is not withholding their wages.

בבא מציעא קי ע”ב: תנו רבנן: האומר לחבירו צא שכור לי פועלים ־ שניהן אין עוברין משום בל תלין, זה ־ לפי שלא שכרן, וזה לפי שאין פעולתו אצלו.

Reb Aharon Steinberg once posed a question: The Torah says, “See, I (Anochi) place before you today a blessing and a curse.” The Baal Haturim says that the word “Anochi” alludes to the first of the Ten Commandments. What does that commandment in particular have to do with this verse?

Also, the Torah promises a blessing if we listen to Hashem – but doesn’t the Gemara say that there is no reward for mitzvos in this world (Kiddushin 39b)?

Furthermore, Hashem Himself follows the Torah’s laws, so how can He postpone our reward, our “wages”, until Olam Haba?

The answer is that Hashem gave the Torah through an agent, Moshe Rabbeinu, and one who hires through an agent does not have to pay on the same day. But the first two of the Ten Commandments were given by Hashem directly to us. Therefore the reward for emunah and renouncing idolatry is paid in this world. Hence, “See that for the mitzvah of Anochi I place before you today, in this world, a blessing and a curse.”

Source: Beis Aharon


Kilayim 9,1: Shaatnez on One Part of a Blanket

Kilayim 9:1. If a garment is made of blended camel’s wool and sheep’s wool, if the majority is camel it is permitted [to mix with linen], and if the majority is sheep it is forbidden. Half and half is forbidden.

Yerushalmi: If a large blanket had shaatnez at one end, and that end was lying on the floor, one may still not cover oneself with the other end.

The Shulchan Aruch Yoreh Deah 301:3 brings this halacha, and the Pischei Teshuva explains that the case is when the entire blanket is sheep’s wool, and there is one thread of linen dragging on the floor. However, if the main blanket is another material, and there is a bit of wool and linen together on the edge, then it is debatable whether the entire blanket becomes forbidden. The Rambam would hold ossur, while the Rosh might hold mutar.

כלאים פרק ט, משנה א: צמר גמלים וצמר רחלים שטרפן זה בזה אם רוב מן הגמלים מותר. אם רוב מן הרחלים אסור. מחצה למחצה אסור.

ירושלמי שם: רבי ניחה בר סבה רבי יוחנן בשם רבי זעירא שאם היה בגד גדול קצתו יש בו כלאים ומונח בארץ ומקצתו אין בו לא יכסה בו מצד השני.

Rabbi Yosef Sayagh heard from a rav in Queens that a young couple once came to him for advice about their baby, who was very colicky and cried all night. Their doctor had no solution. The rav suggested that they check the baby’s blanket for shaatnez. It was found that although the blanket was not wool, it had an appliqué pattern with a picture of a teddy bear, and in that picture there was wool and linen. They removed it, and the baby stopped crying.  

Source: Rabbi Yosef Sayagh

[It seems that just as we have a dispute in the laws of kashrus about whether the rule of חתיכה נעשית נבילה –  a piece containing something forbidden becomes complete forbidden – applies only to milk and meat, or even to other forbidden foods (Yoreh Deah 92:4), there is a similar dispute in the laws of shaatnez. Everyone agrees that if the whole blanket is wool, and there is one thread of linen, one may not cover oneself even with the part that is only wool, because חתיכה נעשית נבילה – similar to a piece of meat cooked with milk. But if the garment is made of polyester, and only the corner has wool and linen mixed, there is a machlokes whether the shaatnez status spreads to the entire blanket.]


Chullin 27b: Is Fishing Tzaar Baalei Chaim?

Chullin 27b: Animals were created from earth, so they need both the esophagus and windpipe cut. Fish were created from the water, so they don’t require any shechitah. Birds were created from the mud, so they only need one tube cut.

Rema Yoreh Deah 13:1: It is allowed to cut a piece off a live fish and eat it, but it is forbidden to eat a whole fish live because of the prohibition, “Do not make yourself disgusting.”

חולין כז ע”ב: דרש עובר גלילאה: בהמה שנבראת מן היבשה ־ הכשרה בשני סימנים, דגים שנבראו מן המים ־ הכשירן בולא כלום, עוף שנברא מן הרקק ־ הכשרו בסימן אחד.

יורה דעה יג,א בהמה חיה ועוף טעונין שחיטה דגים וחגבים אין טעונין שחיטה: הגה ומותר לאוכלם מתים, או לחתוך מהם אבר ולאכלו, אבל אסור לאכלן חיים משום בל תשקצו.

The Hamodia newspaper recently interviewed Rabbi Boruch Cohn, a rebbi in Lakewood who enjoys fishing in local lakes and streams. Their first question was, “Fishing is not known to be a popular downtime activity in our circles. Is there a good reason for this?”

Rabbi Cohn replied, “I don’t have a clear answer to this one, but it might be that people don’t have the time or perseverance to fish; it’s not a pastime for those who want instant gratification! Another reason could be that they’re prone to associate it with hunting, which is assur. When I was thinking of taking up fishing, I discussed the issue with Dayan Yaakov Posen, shlita, of Washington Heights, where I grew up. He advised me that the issur of tzaar baalei chaim (causing affliction to living things) does not apply to fish and gave me an enthusiastic go-ahead. I have since spoken to several Lakewood poskim on this matter, and they are in full agreement with Dayan Posen.” 

(Hamodia, July 8, 2020, Community p. 25)

[Actually, the problem with hunting, according to the Noda Beyehuda (Tinyana YD 10, brought in Pischei Teshuva YD 28:10), is not tzaar baalei chaim, for two reasons:

1) People use the skins, and there is no prohibition on tzaar baalei chaim when the animal is used for the needs of man. The source for this is Piskei Hatosafos Avodah Zarah 11a, explaining why it is allowed to cut the hooves of the king’s horses after the king dies.  

2) There is no prohibition of tzaar baalei chaim when you are killing the animal, only when you are keeping it alive and suffering. This is based on Chullin 7b, where Rabbi Pinchus ben Yair reprimanded Rebbi for owning dangerous white mules. Rebbi proposed cutting their hooves, but Rabbi Pinchus responded that this would be tzaar baalei chaim. Then Rebbi proposed killing them, to which Rabbi Pinchus responded that it would be bal tashchis – wastefulness. From this exchange we see that killing can never be tzaar baalei chaim.

Rather, the problem with hunting is that killing animals for sport is cruelty. We are enjoined to feel that “His mercies are upon all His creatures” and that is why we don’t say bless someone who buys a new leather garment that he should wear it out and buy a new one (Rema Orach Chaim 223:6). Therefore hunting, unless done for a living, may not be strictly forbidden but it does inculcate a bad midah and is not the right thing for a Jew to do.

Furthermore, going out to the forests where the wild animals live is dangerous, and one is forbidden to place his life in danger. Esav was an expert hunter, yet he testified on himself, “Behold I am going to die,” and the Ramban explains that he was likely to die in his father’s lifetime, so he did not need the birthright. One who hunts to make a living is permitted to risk his life, as it says, “He risks his life for it” (Devarim 24:15). But if he doesn’t need the money, it is forbidden.

According to this, it would seem that fishing for sport should exemplify the same bad midah of cruelty as hunting for sport. Tzaar baalei chaim may not apply, but the midos argument still would.

The Noda Biyehuda’s contention that there is no prohibition of tzaar baalei chaim when killing the animal would seem to be against the Sefer Hachinuch 451, who says that the reason for slaughtering at the neck with a perfectly sharp knife is in order to minimize tzaar baalei chaim. According to the Chinuch, we could prove that the prohibition does not apply to fish from the very fact that no shechitah is required.

The nafka minah between the Noda Biyehuda and the Chinuch would be in the question of whether one may make a fish suffer when not killing it. According to the Noda Biyehuda it is forbidden, while according to the Chinuch it is permitted.

Rabbi Menashe Klein (Mishneh Halachos 6:216) was asked whether someone who has an aquarium in his house is obligated to feed the fish before eating a meal. The questioner had brought proof from the fact that one may cut a piece off a live fish, that there is no prohibition of tzaar baalei chaim on fish. R’ Menashe counters that perhaps there really is tzaar baalei chaim on fish, yet eating from a live fish is allowed because the prohibition on causing pain doesn’t apply when using the animal for human needs. We see, for example, that one may cut off and eat a piece of a ben pekuah (a live baby found inside a slaughtered cow) even though it is alive and certainly feels pain (Taz YD 13:3).  

Then he brings a proof that there is indeed tzaar baalei chaim on fish, from the fact that one may not harness two different kinds of fish to his boat (Bava Kama 55a). The prohibition on harnessing two different species is because of tzaar baalei chaim, since an animal does not like to work together with a different kind of animal (Chinuch 550). If this applies to fish, then clearly there is tzaar baalei chaim on fish. He concludes that one must feed his fish before eating a meal (and therefore recommends not keeping an aquarium, lest one transgress this prohibition when eating away from home).

Thus there appears to be an internal contradiction in the Chinuch. If fish have tzaar baalei chaim, then why is it allowed to eat them without shechitah? And you cannot answer, as R’ Menashe Klein does, that for the purpose of man there is no prohibition, because the Chinuch says that even at the time of shechitah we try to minimize pain.

Rather, the answer is probably that the Chinuch’s approach is merely to suggest reasons for mitzvos (often, as in these two cases, more than one reason for each mitzvah), without being particular that everything he says leads to the same halachic conclusions.]   

Bava Metzia

Bava Metzia 76b: The Ill-fated Shabbos Nachamu Getaway

Bava Metzia 76b: Rava said: If someone hired workers to dig ditches, and it rained and filled the land with water such that they were unable to dig, if the workers examined the land the day before and were aware that it might rain, he need not pay the workers. But if they did not examine the land the day before, the owner must pay the workers as much as a worker would accept to agree not to work.

בבא מציעא עו ע”ב: אמר רבא: האי מאן דאגר אגירי לרפקא, ואתא מטרא ומלייה מיא. אי סיירא לארעיה מאורתא ־ פסידא דפועלים, לא סיירא לארעיה מאורתא ־ פסידא דבעל הבית ויהיב להו כפועל בטל. פרש”י סיירא לארעא מאורתא והוליך הפועלים שם וראוה ולא הבינו שהיא לחה או שמא ירדו גשמים בלילה לית להו כלל דהא חזו אינהו גופייהו ועל מנת כן נשתכרו לו. לא סיירוה מאורתא – עליו היה לתת לב לדבר ולהודיעם אם תמצאו שדה לחה לא אתן לכם כלום, ויהיב להו כפועל בטל.

A catering company rented out a hotel in the Catskills and made a Shabbos Nachamu getaway. On Thursday afternoon there was a power outage that lasted until Shabbos, and all the food they prepared got spoiled, or could not be cooked. But the guests already arrived, so they needed something to eat for Shabbos. The catering company rushed out and bought boxes of matza and gefilte fish jars, and that was all the guests had to eat for the whole Shabbos.

Afterwards the guests took the catering company to a Din Torah and demanded their money back. The company responded that they deserved some of the payment, since they had at least given them a Shabbos retreat. The dayan opened up a Yom Kippur machzor and said, “When Yom Kippur falls on Shabbos, some say the words רצה במנוחתינו (accept our rest) and some do not. Your dispute depends on that dispute. Those who don’t refer to Yom Kippur as a day of “rest” hold that a day without eating cannot be restful. The Mishnah Berurah (582:20) paskens like this opinion. Accordingly, a Shabbos without normal, hot food is not a Shabbos, and they do not have to pay.”

Source: Rabbi Hillel David

[It sounds like the psak was that the guests do not have to pay at all. But from our Gemara we see that when an unforeseen accident cancels a job, the workers (i.e. the caterers) must be paid. Only in the case of rain, which is common, and the workers saw the property and realized that rain would make the job impossible, do they lose their wages, since they accepted that risk. But a power outage lasting a whole day is a very rare occurrence which no one expected. Seemingly then, the guests must pay at least some of the price of the getaway.]


Shabbos 66b: A Ruby Prevents Miscarriage

Shabbos 66b: A woman may go out on Shabbos wearing a retaining stone (to help her retain her pregnancy and not miscarry) or with another object that weighs the same as it – even if she has never miscarried in the past, and even if she is not yet pregnant.

שבת סו ע”ב: תנו רבנן: יוצאין באבן תקומה בשבת, משום רבי מאיר אמרו: אף במשקל אבן תקומה. ולא שהפילה ־ אלא שמא תפיל, ולא שעיברה ־ אלא שמא תתעבר ותפיל. ופירש הט”ז או”ח ש”ג כ”ד שטערי”ן שו”ס.

A woman was in the delivery room for hours but could not give birth. The husband called R’ Meir Scheinberg and asked him what to do. Rabbi Scheinberg asked, “Did she take off the ruby from around her neck?” She took it off, and immediately she was able to give birth.

Source: Rabbi Yehuda Aryeh Scheinberg


Sanhedrin 77b: Turning on an Electric Switch on Shabbos

Sanhedrin 77b: Rava said: If a murderer shot an arrow at his victim, and the victim was holding a shield, and someone came and took it away, or even if the murderer himself came and took it away, he is exempt from punishment, because at the time he shot the arrow there was something blocking it.

Rav Papa said: If a murderer tied down his victim and then opened a water stream over him, it is as if he shot an arrow at him and he is liable.

סנהדרין עז ע”ב: ואמר רבא: זרק חץ, ותריס בידו, ובא אחר ונטלו, ואפילו הוא קדם ונטלו ־ פטור, דבעידנא דשדייה ביה ־ מיפסק פיסקיה גיריה.

אמר רב פפא: האי מאן דכפתיה לחבריה ואשקיל עליה בידקא דמיא ־ גירי דידיה הוא, ומיחייב. הני מילי ־ בכח ראשון, אבל בכח שני ־ גרמא בעלמא הוא.

In 1934, Rabbi Chaim Ozer Grodzinski was asked about electric lights on Shabbos. He was shown a journal called Beis Vaad Lachachamim, printed in New York in 1903, in which there appeared a short letter by Rabbi Yechiel Michel Halevi Epstein, author of the Aruch Hashulchan. The Aruch Hashulchan argued that it should be permitted to turn on an electric light on Yom Tov because the fire is already present in the wires. Then he added a second argument that would apply to Shabbos too: when one turns on the switch, he is not creating the fire, only allowing it to reach the bulb, which would be considered “grama” (an indirect action). The Gemara in Shabbos 120b quotes the posuk, “You shall not do any work,” and says, “Doing is forbidden, but indirectly causing is permitted.” Thus one may make a wall of barrels full of water around a fire, so that when the fire reaches them it will be extinguished.

Reb Chaim Ozer explains that the Aruch Hashulchan’s second argument seems to be based on the Gemara in Sanhedrin 77b, which says that the one who took away the shield, allowing the arrow to hit the victim, is exempt. So too, when one turns on a light switch, he is not creating the electric power that goes to the bulb. That power is already in the wires, ready to shoot out. He is just bridging the gap in the circuit.

However, argues Reb Chaim Ozer, the electricity is more similar to the other case in that Gemara, in which someone opens a water stream to kill his victim. The Yad Ramah explains the difference between the two cases: At the time one removes the shield, the arrow is not here yet, but at the time one removes the obstacle in the water stream, the water is pressing up against the obstacle, ready to flow. Here too, the electricity is in the wire ready to flow as soon as the gap is bridged; so it is not “grama”.

Furthermore, even if we were to consider turning on the switch a “grama”, not every “grama” is exempted on Shabbos. The Gemara says in Bava Kama 60a says that winnowing the grain is an act of work on Shabbos, even though the person is just throwing the grain into the air and the wind is doing the job of separating out the chaff. Based on this, the Even Haozer (Orach Chaim 328) argues that pouring wheat into a grinder powered by a water wheel is an act of work (not as the Magen Avraham rules in Orach Chaim 252:20). The rule is that if one is doing the work normally, and the other power helping him (wind, water etc.) is part of his plan, then the Torah categorizes it as work, unlike the case of putting out a fire with a wall of full barrels, which is a unusual method, resorted to on the spur of the moment. Therefore, turning on an electric switch, though it may be “grama”, is the normal way, and would therefore be forbidden.

Source: Achiezer v. 3 siman 60