Let's say that a person has a reason to think his mother might be Jewish (there is some evidence, but only a little), and it is likely that the person will never be able to know for sure. In such a case, does he sin if he is Jewish and does not keep Mitzvot?

Is there a precedent or a standard ruling as to what a person like this should do? Should he convert? Or do you say that maybe it does not matter because if a person is unaware they do not need to follow the law?

(I am not writing about myself even thought I was in such a situation, as I have already made a decision what to do next. It is because I am curious about my family members.)

The question is not about conversion, it is about being unsure about whether one is a Jew and living like a gentile and if that is wrong.

  • 5
    And what's more, some mitzvos — like keeping Shabbos — are forbidden to a non-Jew, so there's no way to be machmir. (Though there is that story (I don't remember where) where the doubtful non-Jew did no melachah except wearing tzitzis which are useless to a non-Jew and therefore only considered carrying when worn by the non-Jew.)
    – b a
    Sep 2, 2012 at 14:51
  • @ba Genius idea!
    – Double AA
    Sep 2, 2012 at 15:45
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    @ba: I've heard that with regards to Avraham Avinu (who we are told kept the whole Torah). There is a disagreement if he had the status of a Ben Noach or a Jew. The question is then, what did he do about Shabbat. If he was not Jewish, he could not keep Shabbat, if he was Jewish, he couldn't break Shabbat. There are actually several answer given to this question by different rabbis over the years. One of them was that he wore tzitzit. - it's been a while, but I'm pretty sure i heard it here: insidechassidus.org/inside-talmud/131-selected-topics/…
    – Menachem
    Sep 2, 2012 at 20:08
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    I think there will be more questions like this as people in countries struck by the Shoah and totalitarism start to dig into their ancestral origins. I think there should be a ruling on this matter by a respectful posek (am I not confusing it?) because the people will ask this question. In Eastern Europe one could be openly Jewish or have a life. It is difficult to get information even from family members who would rather not say, because for so long being Jewish was like a crime. I can see my ancestral surnames on ghetto lists and wonder...
    – MichaelS
    Sep 2, 2012 at 22:54
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    @ba: see about halfway through this rchaimqoton.blogspot.com.au/2006/07/resting-on-seventh-day.html - The answer with the Tzitzit is brought by the Chatam Sofer.
    – Menachem
    Oct 7, 2012 at 3:04

3 Answers 3


The Gemara in Kesubos 15b discusses the status of a child found in the street. Depending on the population demographics of the city, there are different halachos:

אם רוב <עובדי כוכבים> {גוים} <עובד כוכבים> {גוי} אמר שמואל ולפקח עליו את הגל אינו כן אם רוב <עובדי כוכבים> {גוים} <עובד כוכבים> {גוי} למאי הלכתא אמר רב פפא להאכילו נבילות אם רוב ישראל ישראל למאי הלכתא אמר רב פפא להחזיר לו אבידה מחצה על מחצה ישראל למאי הלכתא אמר ריש לקיש לנזקין

Meaning (of the pertinent first line): If it is majority non-Jews, we do not dismiss the possibility that he is a Jew when it comes to saving his life on Shabbos. However, we will feed him non-kosher meat (i.e. we allow him and can even enable him to violate Jewish mitzvos).

If there is a non-negligible but weak indication that a person is Jewish, they still are not obligated to keep the commandments.


If a person is Jewish, he or she is obligated to follow halacha. If a person is not Jewish, he or she is obligated to follow the Noahide laws, and forbidden from doing certain things, such as marrying a Jew, wearing tefillin, or observing Shabbos completely.

For these reasons, it seems clear that a person unsure if he or she is Jewish is obligated to investigate as much as possible to determine whether the person is Jewish. For example, the person should amass whatever family records and genealogical information is available, even if one has to pay for a genealogical service to do this.

If the resulting information still suggests that the person might be Jewish, the person should approach an Orthodox rabbi, or an Orthodox beis din, and ask whether this is good enough evidence for the person's Jewishness.

If the information is not enough to prove the person is Jewish, or it proves the person isn't Jewish, and the person desires to join the Jewish people and become an observant Jew, then the person should pursue Orthodox conversion. If the information points strongly toward Jewishness but was not enough proof, then this may be considered a gerus l'chumra (a conversion done to resolve doubt, for a person who is likely already Jewish.)

  • It would seem that in many cases a chazaka would be in the mix.
    – Yishai
    Feb 14, 2014 at 1:57


Rabbi Leib Tropper is maybe the rabbi most versed in complicated issues of conversion, and I have seen him deal personally with several people who were unsure if they were Jewish. This is what I understood from his response to the above questions:

  • There are precedents, and the standard ruling is as follows:
  • It does matter; even if a person is not sure he is Jewish he needs to follow the law.
  • He does sin if he is Jewish and does not keep Mitzvos.
  • He should convert.

Until he converts, he should make sure to do melacha motzoei shabbes. (Wearing tzitzis may not be enough if there is eruv or maybe even if there is no real reshus harabim.)

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    "maybe"??? Is that really even a possibility?
    – Double AA
    Feb 14, 2014 at 18:54
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    @DoubleAA I believe he meant "even if there is no eruv, if it isn't a real reshus harabim maybe it won't be enough to be considered melacha" i.e. maybe you need to do a melacha d'oraiysa. Feb 16, 2014 at 3:52
  • 1
    @YEZ Wrong "maybe".
    – Double AA
    Feb 16, 2014 at 3:57
  • @DoubleAA Why not?
    – Adám
    Feb 16, 2014 at 16:04

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