RFID tags have very many uses in identifying different objects via radio waves. Recently, libraries have started using them to help keep track of books.

I would imagine that the tags, in themselves, would either be muktzah machmas issur (מחמת איסור), or muktzah machmas chesron kis (מחמת חסרון כיס).

If one were to borrow books from a library that places RFID tags in their books, may these books be read on Shabbos, or is there an issue with muktza?


2 Answers 2


The tags are probably not muktze machmat chesron kis. In order for something to attain that status of muktze, it usually must be quite valuable (ex. a brit milah knife, etc.) so that the only conceivable thing you could do with the object is either prohibited or just not use it at all. (Shulchan Aruch Siman 308.1)

It appears to me however that it does fit quite well with the definition of a kli shemelachto lissur. Of course, then you could move the tag if you needed the space it occupies or needed it for a permitted task.

There is a question whether the book becomes a basis due to the tag-and one standard answer would be no because the tag serves the book not vice versa, as such, whenever we move the book, moving the tag should be okay because it is tiltul min hatzad ldavar hamuter. (See Aruch HaShulchan Siman 309, 5 and 311 21). The distinction here, is that a book would presumably be a kli shemelachto lheter and now you can move the book to protect it.

But are books muktze?

If we are talking about "books of wisdom" (ex. science, philosophy), the Shulchan Aruch brings down a debate (Siman 307 ,17 and 308 50) if we can study from them or move them on Shabbat. See the Mishna Berura that says in Siman 307 there that we are accustomed to be lenient, (hence it would be a kli shemelachto lheter) but says that for a yira shamayim (a God fearing individual) it is appropriate to be stringent.

  • 1
    Muktze machmat chesron kis doesn't have to be extremely valuable. It just has to be something that you are makpid with. The reason a milah knife is considered that isn't because it costs a lot. It's because it is very delicate and easy to break, so you would never use it to cut up some vegetables.
    – Daniel
    Jun 12, 2015 at 14:04
  • You are correct. And perhaps the presentation in my answer could be refined a bit. The point is, it has to be sufficiently valuable in some manner (not necessarily strictly monetary) that you would never consider to use it for something permitted action. The tags spoken about in the question are not costly at all and coupled with the fact there is no reason to make the assumption that someone would only have in mind to use it for a prohibited purpose (in contrast to the bris milah knife), we cannot classify it as muktze machmat chesron kis.
    – Lael345
    Jun 12, 2015 at 14:27

Even according to those who view lighting and extinguishing incandescent light (and comparable electric devices) to be a violation of mavir and mechabeh or boneh and soser, and, resultingly, the light itself, at least in the unlit state,is muktzeh for lack of a shabbos use, it's hard to think of what would be the problem of using a book that has a passive embedded chip (short of the more general issues of shtarei hedyotos about which the general custom is to be lax). In fact, I've never heard of people not wearing electric watches on Shabbos.

  • ....because a watch isn't muktzah, because it has a permitted use, and is being used לצורך גופו. AFAIK, there is no permitted use of an RFID tag.
    – MTL
    Feb 9, 2015 at 14:04
  • It was a little unfair of me to change the question after you posted an answer, but it wasn't any information that I hadn't already told you in comments (I think). ...does your answer explain why an RFID tag isn't muktzah machmas issur or muktzah machmas chesron kis?
    – MTL
    Feb 9, 2015 at 14:06
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    Incidentally, re "I've never heard of people not wearing electric watches on Shabbos": I have. (That doesn't, of course, mean they're right.)
    – msh210
    Feb 10, 2015 at 5:43

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