Vayikra: The Kidneys Advisory
The kidneys are vital organs that essentially act as the body's filtration system, ensuring that toxins are removed from the blood. They are thus responsible for filtering waste products and other excess substances from the blood, which are then expelled in urine. Additionally, the kidneys play a crucial role in maintaining a balance of electrolytes, regulating blood pressure, and controlling red blood cell production through the secretion of hormones, thus making them crucial overall health and function of both man and animal. One of the oft-repeated instructions for ritual sacrifices given in the Book of Leviticus is that the kilayot (“kidneys”) of an animal sacrifice must be burnt on the altar along with various fats from the animal’s body. In fact, of the thirty-one times that the word kilayot appears in the entire Bible, fifteen of those instances refer to this specific rule (Lev. 3:4, 3:10, 2:15, 4:9, 4:7, 8:16, 8:25, 9:10, 9:19). In the essay before you, we explore the etymology of the word kilayot, and compare it to its two possible synonyms in Biblical Hebrew — atzeh and tuchot.
In addition to the word kilayot in the Bible referring to “kidneys” in the anatomical sense, the word is also used in a more abstract sense to refer to one’s innermost thoughts and motives. It is in this cognitive sense that Hashem is said to have the ability to examine man’s heart and kidneys (Jer. 11:20, 17:10, 20:12, Ps. 7:10). In such contexts, the term kilayot is often translated into English as “reins” (which is related to the English words renal and adrenaline).
Besides for the aforementioned instances of kilayot in the Bible, this word also appears in the Mishnah (Chullin 3:2, 4:1, Tamid 4:3). Interestingly, the word kilayot always appears in the Bible and Mishnah in plural form, although theoretically, its singular form should be kilyah. In the Talmud, the Hebrew/Aramaic word kulya refers to “a single kidney” (Pesachim 64b, Chullin 93a, 97a, 126b, 128b–129a, Bechorot 39a, Kritot 14a, 23a).
Rabbi Moshe Tedeschi Ashkenazi (1821–1898) in his work Otzar Nirdafim (§344) connects the word kilayot to the word kele(“jail, incarceration”), spelled with a final ALEPH. He accounts for this connection by explaining that as internal organs, the kidneys are embedded deep within a person’s body, as though they are “hidden” or “jailed’ inside. Indeed, Ibn Ezra (to Ps. 7:10) understands that the term kilayot can sometimes be meant metaphorically as a reference to the thoughts and beliefs “hidden” deep within a person’s consciousness.
In a similar vein, Ibn Ezra (to Ex. 23:25, Lev. 3:4 and Ps. 16:7, 139:13, cited by Radak in Sefer HaShorashim) connects these two meanings of the word kilayot by postulating that the bodily kidneys are the seat of libidinous desire, leading him to explain kilayot as cognate with the verbs derived from the root KAF-LAMMED-(HEY) that refer to “desiring/longing” in the Bible (II Sam. 13:39, Ps. 119:3, 119:81). Asimilar point is made by Rabbi Samson Raphael Hirsch (to Ex. 23:18 and Lev. 3:4), who writes that the kidneys are the most profound source of sensuous desire, making them the organs of the evil inclinations and impulses. In line with this, Nachmanides (to Lev. 1:9) writes that burning the kidneys on the altar is so central to the sacrificial rites needed to achieve atonement squarely because the kidneys are instruments of the sort of desire that cause sin in the first place.
When foretelling of the especially-good crop that will be produced by the Holy Land after the Jews conquer that land, Moses refers to “the fat of kidney-wheat [chelev kilyot chitah]” (Deut. 32:14). Rashi (to Deut. 32:14) explains that this refers to especially fatty wheat that was as plump as a kidney. Although Rashi (there) sees this prediction as having come to fruition in Solomonic Times, the Talmud (Ketubot 111b) sees this as a reference to the future Messianic times, when the Holy Land will produce wheat kernels that are as big as the kidneys of a large ox. Chizkuni (to Deut. 32:14) explains the term kilyot in chelev kilyot chitah as referring to the “choicest” type of wheat, given that kilayot can refer to one’s innermost wants and desires, and not just to the physical kidneys. Alternatively, Radak (in Sefer HaShorashim) explains that because wheat kernels somewhat resemble the shape of kidneys, they are called kilyot chitah (much like in English “kidney beans” are called so because they resemble the shape of the anatomical kidney).
In his work Cheshek Shlomo, Rabbi Shlomo Pappenheim of Breslau (1740–1814) traces the word kilayot to the biliteral root KAF-LAMMED, which he defines as “totality/all-encompassing.” The most obvious manifestation of that meaning is the word kol (“all,” “every”), although Rabbi Pappenheim lists a whole bevy of words as deriving from this biliteral root and its tributaries. For our purposes, it is sufficient to note that he explains the word kli ("vessel") as a derivative of that root. He explains that kli denotes a receptacle into which things may be placed, such that they are surrounded all around by the container. Based on this, he explains that kilayot are called such because they function like a kli in that they store waste filtered through the blood until such time that they can be expelled in one’s urine. [In previous essays, I elaborated on this two-letter root and its derivatives, the most recent of those is “On Misers and Cheapskates” (June 2022).]
In one particular passage, the Bible stipulates that with animal sacrifices, one should remove the fat from opposite the atzeh (Lev. 3:9). This word atzeh only appears once in the Bible, thus making it a hapax legomenon. Yet, Rashi (to Ex. 29:22, Lev. 3:9) and Rashbam (to Lev. 3:9) explain that atzeh means the same thing as kilayot. From where does Rashi’s explanation come?
The Talmud (Brachot 61a) teaches that the two kidneys provide eitzah ("advice") to the heart, with one kidney advising a person to perform good and the other, to perform evil. The Talmud (there) further posits (based on Ecc. 10:2) that the kidney on the right advises for the better, while the kidney on the left advises for the worse. When citing this tradition, Rabbi Elazar Rokeach of Worms (late 12th century Asheknazic scholar) in Sodi Razi adds that the kidneys are also the source of happiness, as it says “and my kidneys shall rejoice” (Prov. 23:16).
Based on the Talmudic tradition, the Talmud (Chullin 11a) explains that the aforementioned Biblical term atzeh refers to none other than the "kidneys," which are the anatomical body part that are said to provide eitzah. This explication of the word atzeh — which clearly serves as the basis for Rashi’s understanding of azteh as synonymous with kilayot — seems to be based on spelling of atzeh as AYIN-TZADI-HEY, which can also be read as eitzah.
Rabbi Shet ben Yefet HaRofeh of Aleppo (Chemat HaChemdah to Lev. 3:17) explains that the kidneys are called atzeh because they filter the blood and cleanse the flesh, thus allowing the head and heart to properly function. This, in turn, enhances a person's cognitive processes akin to receiving "good advice." Alternatively, he posits that atzeh can be interpreted literally as the “marrow” inside a bone, and by way of analogy refers also to the “brain” inside the skull and the “kidneys” inside the body. Additionally, we may explain that the kidney is referred to as an atzeh because its primary function is to filter the blood, much like how giving advice assists individuals in filtering good ideas from bad ones. [For more on the scientific connection between a person’s thoughts in their kidneys and how this might relate to kidney transplants, see Rabbi Natan Slifkin’s monograph “The Question of the Kidneys’ Counsel.”]
Despite all of this, it should be noted that reading atzeh as “kidney” is not unanimously agreed upon. As a matter of fact, a contingent of prominent commentators explains the word atzeh as “the end of the spine.” These important sources include Targum Onkelos (to Lev. 3:9, see Melechet Shlomo to Chullin 3:1), Sefer He’Aruch, Sefer Tishbi, Ibn Janach, and Radak. The latter two sources trace the word atzeh to the triliteral root AYIN-TZADI-HEY (although Radak admits that Chazal evidently saw its root as YOD-AYIN-TZADI, per the atzeh-eitzah connection mentioned above).
Ibn Ezra (to Lev. 3:9) acknowledges that the word atzeh only appears once in the Bible, asserting that its meaning may be gleaned from its context — without explaining what that meaning might be. What Ibn Ezra does clearly say is that he does not accept those who explain the word atzeh as related to the word eitz (“tree”). Such an understanding is, however, implied by Machberet Menachem, who lists the word atzeh as a derivative of the biliteral root AYIN-TZADI. Indeed, Rabbeinu Bachaya (to Lev. 3:9), Shadal (there), and Rabbi Pappenheim write that atzeh relates to eitz because the structure of the spine and its tributaries resemble the trunk and branches of a tree.
Finally, we turn to the word tuchot, which only appears twice in the Bible. When King David articulated Hashem’s demand that belief in Him be held even in one’s heart of heart, he said: “Behold, in truth You desire [our belief in You to be] in our tuchot” (Ps. 51:8). Similarly, when Hashem revealed to Job the different ways that He contributes to the world, He rhetorically asked, “Who placed wisdom in the tuchot? Or who gives understanding to the sechvi?” (Job 38:36). The classical commentators (including Targum, Rashi, and Radak there) follow the Talmud (Rosh HaShanah 26a) in explaining that tuchot refer to the “kidneys.” Like the word kilayot, tuchot also only appears in the plural form and never in the singular form in the Bible.
Ibn Ezra (to Job 38:36) differs from this slightly, preferring to explain tuchot more generally as “innards,” and not specifically as the “kidneys.” But it’s the same basic idea.
There are two ways to understand how tuchot in the sense of “kidneys” or “innards” relates to the root TET-(VAV)-CHET: Machberet Menachem and Rashi (to Ps. 51:8 and Rosh HaShanah 26a) explain that the kidneys are called tuchot from the root TET-CHET, which refers to something “smooth.” Another word derived from that root is mitachavei (Gen. 21:16), which means “target,” as when one shoots at one’s target, one aims in such a way that there will be a “smooth” uninterrupted trajectory for the projectile to reach its intended mark. Similarly, Radak (in Sefer HaShorashim), Rabbi Avraham Ibn Ramoch (to Ps. 51:8), and Metzudot Zion (to Ps. 51:8) explain tuchot relates to the “smeared” meaning of TET-CHET, and refers to the fact that the kidneys are covered in fat, as though smeared in that substance (see Chochmas Manoach to Rosh HaShanah 26a who merges these two explanations).
Others explain that tuchot refer to “fowl” (like an ibis or some other bird), or to “darkness.” See Da’at Mikra (to Job 38:36), as well as the Brown-Driver-Briggs Hebrew lexicon and David J. A. Clines' Dictionary of Classical Hebrew. Part of the question relates to the meaning of the word sechvi (used alongside tuchot in Job), i.e., whether it means “heart” or “rooster.” I discussed that particular word in a previous essay entitled “Welcome to Rooster City” (July 2021).
