Inspired by R' Slifkin's new monograph, Wrestling with Demons, and acknowledging the fact that the existence of sheidim and other things magical in nature is an age-old dispute, I am wondering about the following question:

What halachic and/or customary practices would be affected by one's belief in demons? That is: I am looking for examples of halachos or minhagim that people observe that are dependent on the literal existence of sheidim, such that if one denied their existence, these laws/customs would be irrelevant.

  • You ask which "practices would be affected by one's belief" and which "would be irrelevant" (emphasis added). Do you mean to ask which practices actually are dropped by those halachic authorities who discount shedim, or do you mean to ask also which ones merely 'should' be so dropped (even if perhaps they are in fact kept, perhaps because they are entrenched customs)?
    – msh210
    May 23, 2011 at 18:49
  • I meant which practices 'should' be irrelevant, even if perhaps people might observe them anyway. If there are halachic authorities who mention it, all the better.
    – jake
    May 23, 2011 at 18:56
  • Demons do not exist
    – Jonathan
    Dec 22, 2019 at 20:21

5 Answers 5


Some people are careful to spill off a little bit of water (and other liquids?) before drinking, a practice explained in the Gemara (Chullin 105b, bottom) as due to concern that a shed may have drunk from it. However, most people don't worry about it.


We don't keep the halachos in the gemara about zugot (pairs), a demon-related issue.

  • Don't we? I grew up with the understanding that we don't boil an even number of eggs at a time.
    – msh210
    May 24, 2011 at 3:36
  • 3
    @msh: my understanding was that this is because of kashrus considerations (in case some of them turn out to have blood spots, they can be nullified by the majority), not because of zugos.
    – Alex
    May 24, 2011 at 3:53
  • @Alex, that explains why not to boil one or two eggs, not why not to boil four or six. Unless I'm missing something?
    – msh210
    May 24, 2011 at 3:58
  • 2
    @msh210: true, technically it should just require us to boil three eggs or more together. It looks like people have incorrectly generalized that it should always be an odd number, though. Be that as it may, it doesn't seem to be related to zugos, because that would apply to eating the eggs, not to their preparation.
    – Alex
    May 24, 2011 at 15:41
  • 1
    See also judaism.stackexchange.com/q/12644.
    – msh210
    Jul 20, 2012 at 21:21

What about the "Birchat Me'ein Sheva" at the end of the friday night prayers? Shulchan Aruch says that this was added so that the people in the synagogue should have extra time to finish their prayers, so that they could walk home together. The sages were worried about "Mazikim" (usually understood to be demons).

Here's a link to the Paragraph in the Shulchan Aruch Harav: Siman 268 Se'if 13

  • 5
    One could understand mazikim as demons, but one could also understand it as other rural dangers like the Rambam does, as he brings this takana (Hil. Tefilla 9:11) even though he presumably does not believe in sheidim.
    – jake
    May 23, 2011 at 22:53
  • Is that the same logic used by the Shibolei Haleket in saying azkaros before sh'mone esrei of ma'ariv "for protection"?
    – WAF
    May 24, 2011 at 2:12

Washing hands repeatedly in the morning to dispel the bad spirit on them. (Some perform this ritual after sleeping in the daytime as well).

This is stated in the Gemara Shabbos 108b-109a:

הוא היה אומר יד לעין תיקצץ יד לחוטם תיקצץ יד לפה תיקצץ יד לאוזן תיקצץ יד לחסודה תיקצץ יד לאמה תיקצץ יד לפי טבעת תיקצץ ידלגיגית תקצץ יד מסמא יד מחרשת יד מעלה פוליפוס תניא רבי נתן אומר בת חורין היא זו ומקפדת עד שירחוץ ידיו ג' פעמים

This article on the Seforimblog cites the opinion of R. Abadi who writes:

That he is inclined to rule – ולולי דמסתפינא הייתי אומר להלכה למעשה – that the entire practice of negel vasser is no longer relevant to us because ruah ra’ah is no longer a concern.

This avoids the question of whether demons ever existed, noting only that now they apparently do not.

It should be noted that there would still be an obligation to wash one's hands, but it would not require repetition. According to the Rosh the reason for washing is for cleanliness before prayer (besides for the matter of spirits). Accordingly, ritual repetition would be unnecessary.

  • Oddly enough it makes matters worse for his case. But I got mixed up before. Shivsa is the one Tosafos and Rashi argue about . Yoma 77b. There Tos says not to worry about shivsa cause they don't have it in their country. But everyone Shulchan Aruch included say to do 3 times. And all more recent poskim too. I'm not going to rescind on my up vote, but had I known these two sources were coming, I wouldn't have voted up.
    – user6591
    Jul 9, 2015 at 1:57

Adapted from my question here. TLDR: not doing dangerous things during the Nine Days is predicated on the existence of demons.

There are various restrictions in place from Rosh Chodesh Av for Ashkenazim and just during the week of Tisha B'Av for Sefardim. These are discussed in OC 551.

The relevant portion is the final halacha in the siman, halacha 18:

צריך ליזהר מי״ז תמוז עד ט׳ באב שלא לילך יחידי מד׳ שעות עד ט׳ שעות משום שבהם קטב מרירי שולט ולא יכו התלמידים בימים ההם

One must be careful from 17 Tammuz to 9 Av not to walk alone from the fourth to ninth hours of the day, when Ketev Meriri rules, and one should not hit his students during these days.

(For the curious, Ketev Meriri is a demon discussed in Pesachim 111b, Midrash Tehillim 91, Eichah Rabbah 1:29, Bamidbar Rabbah 12:3, Yalkut Tehillim 842, and Tanchuma Nasso 23. [...])

What's wrong with these activities that they are forbidden during this time of year? This is sourced in the above Eichah Rabbah and Tanchuma Nasso, which describe the havoc wreaked by Ketev during this time period. Accordingly, one should avoid doing things that are dangerous, lest one tempt Ketev to finish him off. The Midrash cites the example of a man being chased by another wielding a wooden stick. The latter was stopped by R' Avahu, who, seeing Ketev chasing him with an iron stick foresaw that were the man to beat his fellow with the wooden stick, even though he didn't intend to kill him, Ketev would continue the beating and kill him. For similar reasons, a teacher may not hit a student [...], for fear of inciting the demon on the child.

It's for this reason that one may not do anything dangerous during these days (R' Moshe in Shmaytsa d'Moshe, p. 428; R' Wozner in Kovetz MiBeis Levi, Bein HaMetzarim p. 11 sec. 12; et. al.).

(The parameters of this are discussed further and form the basis of my question linked.)

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