Age is a very important part of Jewish Halakha, with many dates being critical for one's responsibility, including Misos Beis Din (capital punishment). E.g. 3 year old girl can be betrothed and a male adulterer be killed for having relations with her (she is exempt as an Oneis till 12); 12 year old girl and 13 year old boy are liable for capital transgressions such as Shabbos, Avodah Zara.

I could not, however, find any obligation on a father or a mother or oneself or a Beis Din to keep track of someone's age. If so, how one is supposed officially to know his/her age? Birthdays in Judaism discusses celebrating, but not the necessity of knowing one's age.

Some say pubic hair are a sign, but this is only an approximation. Imagine two witnesses testify on someone transgressing Shabbos, but who's testifying on his age?

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    A father is trusted to say that X is his son, even though he's (obviously) related to X.
    – Double AA
    Oct 28, 2017 at 23:06
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    What (or who) is "Beilah" (4th line)? I'm trying to follow the transliteration, but, I'm a bit lost. If you would, please translate some of the "yeshivish" terms into English.
    – DanF
    Oct 29, 2017 at 2:12
  • These days, everyone has a birth certificate. It's quite reliable, though, technically, someone could forge one. In the worst case, why can't a child or adult just look at that document and figure it out? Eventually, of course, once you reach a certain age, dementia may set in. If that happens, even if someone trustworthy tells you your age, it may not matter. Seems that you're asking 2 questions - 1) Is there an obligation for a parent to keep track, and 2) how does someone know. I think I've answered the 2nd question.
    – DanF
    Oct 29, 2017 at 2:19
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    I don't know if Moshe (or anybody else) was obligated to keep track of his age but, nevertheless, he did; "Today, I am one hundred and twenty years old" (Deut. 31:2). I hope you too keep track of your age. (Can't wrap my head around how things would be otherwise: Beit Din: "Why didn't you circumcise your son on the eighth day?" Father: "I didn't know old he was." Beis Din: "He was just born last week! How could you forget how old he was?" Father: "Well, nobody told me I'm obligated to keep track of his age.")
    – Oliver
    Oct 29, 2017 at 20:34
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    @DonielF Yes, situations like that do exist. I'm assuming this person never had a Bar / Bat Mitzvah (celebration, etc.)? I guess in such cases, one needs to approximate. Somehow, when you reach 50, either your body or your doctor is pretty quick to tell you your age :-)
    – DanF
    Oct 30, 2017 at 2:57

1 Answer 1


There is no obligation to have Eidim (two male witnesses) present at every birth, as we are not trying to kill as many people as possible with Misos Beis din(death penalty). This is because the Gemoro Makos 7a says:

סנהדרין ההורגת אחד בשבוע נקראת חובלנית רבי אליעזר בן עזריה אומר אחד לשבעים שנה -
A Sanhedrin that executes a transgressor once in seven years is characterized as a destructive tribunal. Rashi explains - If you would have done this you would have increased murder in Isreal because people would no longer fear court.

And when we don't have eidim to prove his age, we cannot kill him:
Kesubos 15a says:

ספק נפשות - דיני נפשות להקל דהא והצילו העדה כתיב- במדבר לה- it is written in Bamidbar 35:"The Congregation (sanhedrin) shall save" - Death penalty is judged leniently when in doubt - which means until we have full proof with Eidim we cannot kill the subject to death.

So how can we ever put someone to death?
The answer is that when there are Eidim that know the boy has been in the world for 13 years (and 1 day) and the girl for 12 years (and 1 day) only then do we implement death penalty.
For example the eidim were invited to the Shalom zachor (thanksgiving lechaim) the following friday night after birth on wednesday night the first citing of that boy. When this boy is 13 years and 1 day later Beis din can only now Kill him if he has שתי שערות (two hairs of puberty), and is Mechallel Shabbos. Even though he is really 13 years and 3 days. The same would apply for a girl born earlier in the week and the eidim saw her at the kiddush next shabbos morning. However with regards to a woman, if she gave birth in front of eidim absolutely no proof is needed for her age (see backround info below) and she gets Misas beis Din. see Shulchan Aruch Even Haezer 155,12-14:

Bottom line: When there is doubt of age one is always strict e.g saphek Kiddushin requires a Gett, Saphek gittin she's ossur to Kehuna, Saphek Dinei Nefashos (i.e we have to be lenient not to kill them see above) we only know for sure how long he's been alive with proof of Eidim.

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    Isn't it weird? So many Halokhos deal with age and there's no approach whatsoever to monitor it. Doesn't it make the laws theoretical and not practical?
    – Al Berko
    Dec 17, 2017 at 22:04
  • My question was not about what do we do in Sofek. We know what to do. But how come the Sages did not provide us with an obligatory system to minimize it?
    – Al Berko
    Dec 17, 2017 at 22:10
  • @Al Berko if we obligate eidim to be present at the birth even though this will minimize saphek kidushin/gittin cases which is good, the flipside is that we are providing grounds for more people would get killed which the Beis din Avoid at all costs as it says in Makkos 7a "a Beis din that killed more than 1 in 7/70 years is a murderous Beis din"
    – user15464
    Dec 18, 2017 at 14:52
  • @Al Berko see my ammended version that incoorperates your point
    – user15464
    Dec 18, 2017 at 15:02
  • @AlBerko This could be generalized to an obligation to keep track of the passage of time for things other than people and the mitzvos that involve them, correct? E.g. When the Torah says "כבש בן שנה" does that form an obligation to keep track of the animal's age or just require that it meet the criterion when the time comes (as I think is the simpler way to interpret such rules)?
    – WAF
    Dec 19, 2018 at 13:00

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