Mishna B'rura 264:1 says:

The reason for the invalidity of [certain] wicks and oils [for the Shabas lights] is that they do not shine well and we're afraid he may tilt the lamp so the oil within it will flow toward the wick so it will light well, and he'd be liable for [the m'lacha of] burning.

This applies not only to Shabas lights, but to any oil lamp one may read near (MB 673:6). If he did light such a lamp, there are circumstances in which he may not use it (Rama 264:1).

Lighting an incandescent bulb is generally accepted as being forbidden mid'oraysa AFAIK. A bulb not seated properly in its socket will sometimes flicker. It seems reasonable to me that one should not be allowed to leave such a light (i.e. an incandescent bulb flickering due to not being seated well) on on Shabas, and, if he did leave it on, that he should not be allowed to use it under certain circumstances, just as with certain oil lamps. Do any pos'kim discuss this case? What do they say?

  • Misvara it seems like it should be okay, because there's no chashash of "tilting" (though perhaps one would be tempted to screw it in).
    – user3318
    Commented Dec 5, 2013 at 1:26
  • Also, it's not obvious from the MB that the issur of actually lighting such a light applies to all lamps. Perhaps it only applies to lamps which must be lit for mitzvah purposes, because since one must light it anyway the Rabbis required one to do it in the "safest" way possible. I think that reading would be consistent with the text of the MB.
    – user3318
    Commented Dec 5, 2013 at 1:28

2 Answers 2


In Shmirat Shabbat K'Hilchato in 13:32 he discusses using a dimmer - and permits it, though he recommends covering/taping up the switch.

In the footnote (112) he says that since light bulbs do not flicker, there's no issue with "fixing the wick". He has some sources there which I did not follow up on.

It would seem that he would not allow the use of flickering light bulbs without conforming to the laws of Shema-Yateh.

I do recall reading that in Kollel Chazon Ish in Bnei Brak they appoint to Shomer on Friday night, so that everybody can read using the lights - even though they are very high up. Seems that they do not differentiate between electricity and oil.

However, neither the Shmirat Shabbat K'Hilchatonor the Orchos Shabbat mention this opinion but I found a reference to it here:

גם בזה דעת החזון איש שיש על אור החשמל דין של נרות שצריך "שומר" לצורך השתמשות ביחיד לאורו, אך דעת רוב הפוסקים וכן המנהג שלא להצריך שומר כיון שאין אפשרות להטות את האור

His source being:

דעת החזו"א הובא בספר דינים והנהגות (פ"ט סל"ב) שכך היה מתנהג הלכה למעשה

  • 3
    Thank you; but the Chazon Ish's view (according to the Din page you link to) seems to be about all electric lights, not only those that visibly flicker. While obviously he'd hold that flickering ones are also forbidden, I still wonder whether anyone forbids flickering ones specifically. As you note, the SSK possibly does. +1, anyway.
    – msh210
    Commented Dec 11, 2013 at 8:18

There is no problem having your machinery, whatever it is exactly, working for you on shabbos. if someone left it on before shabbos, there would be no problem with any sort of bulb as long as no one is the direct or indirect cause of the flickering.

Essentially the only time you're 'ovair', "guilty" so to speak, of breaking shabbos is when you actively perform an action, except in a few specific cases and if i'm not mistaken I believe they aren't shabbos related (see "lav sh'ayn bo mei'seh", a Sin Without Doing an Action).

I hope this helps!! Let me know anything else I can do to help!

  • 4
    This misses the crux of the question, namely that it is assur to leave some machinery working as described in the sources brought by the OP.
    – user3318
    Commented Dec 4, 2013 at 20:59
  • The MB states that only TILTING the lamp is the m'lacha of burning. When he is not doing any tilting or any action at all, why would you think he would be liable for that m'lacha? Commented Dec 5, 2013 at 0:40
  • 2
    I didn't say he's liable for a m'lacha. I said it's assur to leave the lamp burning. It's a separate rabbinic issur -- see MB 673:6.
    – user3318
    Commented Dec 5, 2013 at 1:21

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