The first mishna in Parah talks about the age that a cow can be and still be valid as a parah adumah:

רבי אליעזר אומר עגלה בת שנתה ופרה בת שתים וחכ"א עגלה בת שתים ופרה בת שלש או בת ארבע ר"מ אומר אף בת חמש כשרה הזקנה אלא שאין ממתינין לה שמא תשחיר שלא תפסל

R' Eliezer says a calf is in its first year, a cow is in its second year. The Chachamim say a calf is in its second year, a cow is in its third year. R' Meir says even an old cow in its 5th year is ok, but we don't wait because it might grow black hairs.

The first parah adumah was done on the second of Nissan (Rashi in several places but I can't find them now). This means that the cow was born in Egypt. According to R' Eliezer, it could have been born as late as Rosh Chodesh Nissan of החדש הזה לכם (which is a nice connection to reading Parah the week before Hachodesh). According to the Chachamim and R' Meir, it was born before the plagues even started! Either way, how did its owner know to treat it specially and not accidentally disqualify it by putting something on it?

Several suggestions:

  • A younger cow can be used bedieved? The Rash and Tosfot Yom Tov on that mishna suggest that an older cow is ok bedieved even according to R' Eliezer, so maybe a younger one is too. But I haven't found anyone who says so explicitly, and the Rambam at the beginning of Hilchot Parah strongly implies that it's not.

  • The owner had no idea, but Hashem made a miracle that nobody ever ended up putting any burdens on it? It's possible, but then how did the owner remember that he hadn't done it without thinking, since he would have had no reason to think about it?

  • It was a wild cow that Hashem caused to wander into the camp? Again this raises the same question - how did anyone know that it had never had a burden on it?

  • Hashem told the owner of the cow to be careful with it through a private, unrecorded nevuah? (According to the Chachamim/R' Meir it would have to be through Miriam or Aharon or someone else, since Moshe was still in Midyan.) This would need a very strong source.

  • 1
    "Again this raises the same question - how did anyone know that it had never had a burden on it?" If it was wild, wouldn't it have a Chazaka? But then you need Rov cows to be wild, which seems ... unlikely. Then again, Moshe could have had a Navua about this cow that wandered in. If you want a lomdishe answer, I'm sure you could make the argument that work done before Matan Torah doesn't disqualify.
    – Yishai
    Sep 1, 2016 at 14:04
  • Good question! Re points 2 and 3, the disqualification of "being worked"/"having a yoke put on it" has an element of intent - as seen in mishnayos 2:3,4 - in that if the load it has borne was for its own benefit it is not disqualified. So perhaps that should help somewhat with establishing its fitness or building up a chazaka.
    – WAF
    Sep 1, 2016 at 14:31
  • If the Para Aduma was with Bnei Israel from the being, how can you explain the fact the very first time the Para Aduma was mentioned was in Parsha Chukas.
    – user13289
    Sep 2, 2016 at 15:09
  • The first time techeilet is mentioned is in Terumah. Does that mean they didn't have any blue dye up to that point? And, even setting aside midrashim about Marah or the second of Nissan, it's clear from the story of Pesach Sheni in Behaalotcha that there was a parah adumah before Pesach Sheni, at the latest.
    – Heshy
    Sep 2, 2016 at 15:49
  • Also consider the meforshim that parah adumah was one of the mitzvos given at Marah on the way to Har Sinai (right after krias yam suf) Sep 2, 2016 at 16:33

2 Answers 2


I remember an aggada in which a gentile sold a Para Aduma to the Sanhedrin and put a yoke on it just before he delivered it. The chachamim were able to tell that he had done so because it broke certain hairs on the back of its neck and those hairs would never grow back in the same way. I do not recall the source of this aggada, but it could point to the reason that they could tell (at Mara) that a cow had not been used.

Another reason could be that since the halacha of Para Adumah was given at Mara, they could have separated out calves of the appropriate ages (which would have been too young to use for work) so that they could be used when they became old enough (the following Rosh Chodesh Nisan).

The youngest calf according to Rav Eliezer would have been born just before the first Rosh Chodesh Nisan before they left Mitzraim so that it entered its second year the Adar after Marah. It would have definitely been too young to have any burden put on it before Marah, and the halacha was known after that so it would have been watched. According to the Chachamim (in its third year), it would have been born the year before the Exodus. Here too, by the time it was old enough to "bear a burden" the plagues would have started and Bnei Yisrael would not have been using the young animals for work.

The owner would certainly remember what he had done with the animals under his control because of the "work stoppage" entailed by the plagues and the Exodus.

  • I like the piece about the hairs. I'm not convinced about not putting anything on it because of the "work stoppage." Maybe you needed to bend down to tie your shoe, so you put your keys or whatever you're carrying on the calf's back for a second. It's completely unremarkable and you wouldn't think twice, or remember it more than 2 minutes later, if you don't have a particular reason to.
    – Heshy
    Sep 1, 2016 at 14:48
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    מילתא דלא רמיא עליה דאיניש לאו אדעתיה
    – Double AA
    Sep 1, 2016 at 18:17

Perhaps the law only kicks in when it's given (i.e. at Marah and/or at Sinai) and is not retroactive, such that all red cows at the time of matan torah are eligible even if they worked the day before. Alternatively, perhaps because the Egyptians revered their livestock, there was at least a population of cows that were known to have never been used.

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