From this answer:

The Rambam (Bias Mikdash 6:7) states clearly that a Kohain whos Kidney was removed is NOT considered a Baal Mum.

אֵין פּוֹסֵל בָּאָדָם אֶלָּא מוּמִין שֶׁבְּגָלוּי. אֲבָל מוּמִין שֶׁבַּחֲלַל הַגּוּף כְּגוֹן שֶׁנִּטַּל כֻּלְיָתוֹ שֶׁל אָדָם אוֹ טְחוֹל שֶׁלּוֹ אוֹ שֶׁנִּקְּבוּ מֵעָיו אַף עַל פִּי שֶׁנַּעֲשָׂה טְרֵפָה עֲבוֹדָתוֹ כְּשֵׁרָה שֶׁנֶּאֱמַר (ויקרא כא יט) "שֶׁבֶר רָגֶל אוֹ שֶׁבֶר יָד" מָה אֵלּוּ בְּגָלוּי אַף כּל בְּגָלוּי: ‏

But according to wikipedia,

The first successful nephrectomy [= kidney removal] was performed by the German surgeon Gustav Simon on August 2, 1869 in Heidelberg.

So how did the Rambam know it was possible?

(The Kesef Mishneh brings the Rambam's sources as the Mishna and Tosefta, but neither gives the kidney example.)

  • 1
    Maybe the Rambam’s just talking theoretically? The Gemara talks about one who undergoes other surgeries without providing evidence that they’re possible (or impossible, in some cases). As a doctor he may have known it was theoretically possible even without having performed it or without knowing of someone who did.
    – DonielF
    Nov 5, 2018 at 17:00

1 Answer 1


The Rambam didn't know a successful kidney removal was possible. He was working under the assumption that anyone whose kidney was removed would necessarily die soon.

The Rambam's source is Bechorot 7:7, which discusses which blemishes render an animal unfit for eating, but not a person for priestly duties:

אלו כשרין באדם, ופסולין בבהמה: אותו ואת בנו, וטרפה, ויוצא דופן, [ ושנעבדה בהן עבירה, ושהמית את האדם ].

The Rambam's own commentary to the Mishnah makes it clear he thought such a blemish would be fatal:

וטרפה הוא שאירע בו חולי ממית כנקובת המרה והמעים וכיוצא בו מאשר מצינו באלו טרפות

Following the Mishnah (Chulin 3:1) regarding an animal:

כל שאין כמוה חיה טרפה

  • i wonder if the Rambam should be read that a man and animal share the same chances of dying from similar wounds/defects? OR, its a Halachic status. OR, a man could merely "possibly" become a treifah if his kidney is removed, OR he was referring to the possibility of becoming a treifah if, for instance his 2nd kidney were the one removed? either way +1 Nov 5, 2018 at 17:23

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