In the Torah, we first encounter "dolphin skins" (עֹרֹת תְּחָשִׁים), the usual English rendering, in Parashat Terumah:
(א) וַיְדַבֵּ֥ר יקוק אֶל־מֹשֶׁ֥ה לֵּאמֹֽר׃ (ב) דַּבֵּר֙ אֶל־בְּנֵ֣י יִשְׂרָאֵ֔ל וְיִקְחוּ־לִ֖י תְּרוּמָ֑ה מֵאֵ֤ת כׇּל־אִישׁ֙ אֲשֶׁ֣ר יִדְּבֶ֣נּוּ לִבּ֔וֹ תִּקְח֖וּ אֶת־תְּרוּמָתִֽי׃ (ג) וְזֹאת֙ הַתְּרוּמָ֔ה אֲשֶׁ֥ר תִּקְח֖וּ מֵאִתָּ֑ם זָהָ֥ב וָכֶ֖סֶף וּנְחֹֽשֶׁת׃ (ד) וּתְכֵ֧לֶת וְאַרְגָּמָ֛ן וְתוֹלַ֥עַת שָׁנִ֖י וְשֵׁ֥שׁ וְעִזִּֽים׃ (ה) וְעֹרֹ֨ת אֵילִ֧ם מְאׇדָּמִ֛ים וְעֹרֹ֥ת תְּחָשִׁ֖ים וַעֲצֵ֥י שִׁטִּֽים׃
(1)יקוק spoke to Moses, saying: (2) Tell the Israelite people to bring Me gifts; you shall accept gifts for Me from every person whose heart is so moved. (3) And these are the gifts that you shall accept from them: gold, silver, and copper; (4) blue, purple, and crimson yarns, fine linen, goats’ hair; (5) tanned ram skins, dolphin skins, and acacia wood;
Apparently, the people have "dolphin skins". Where occasionally mentioned in the Torah (more on that below), the Hebrew spelling is rendered in the plural and later in the singular (examples):
(יד) וְעָשִׂ֤יתָ מִכְסֶה֙ לָאֹ֔הֶל עֹרֹ֥ת אֵילִ֖ם מְאׇדָּמִ֑ים וּמִכְסֵ֛ה עֹרֹ֥ת תְּחָשִׁ֖ים מִלְמָֽעְלָה׃ {פ}
(14) And make for the tent a covering of tanned ram skins, and a covering of dolphin skins above.
(לד) וְאֶת־מִכְסֵ֞ה עוֹרֹ֤ת הָֽאֵילִם֙ הַמְאׇדָּמִ֔ים וְאֶת־מִכְסֵ֖ה עֹרֹ֣ת הַתְּחָשִׁ֑ים וְאֵ֖ת פָּרֹ֥כֶת הַמָּסָֽךְ׃
(34) the covering of tanned ram skins, the covering of dolphin skins, and the curtain for the screen;
(ח) וּפָרְשׂ֣וּ עֲלֵיהֶ֗ם בֶּ֚גֶד תּוֹלַ֣עַת שָׁנִ֔י וְכִסּ֣וּ אֹת֔וֹ בְּמִכְסֵ֖ה ע֣וֹר תָּ֑חַשׁ וְשָׂמ֖וּ אֶת־בַּדָּֽיו׃
(8) They shall spread over these a crimson cloth which they shall cover with a covering of dolphin skin; and they shall put the poles in place.
"Dolphin skin(s)" is curious and described in different ways. The Rabbis of the Talmud note that it comes from an animal known to Moses and afterwards no longer extant, with its identity remaining unknown:
מַאי הָוֵי עֲלֵהּ דְּתַחַשׁ שֶׁהָיָה בִּימֵי מֹשֶׁה? אָמַר רַבִּי אִלָּעָא אָמַר רַבִּי שִׁמְעוֹן בֶּן לָקִישׁ, אוֹמֵר הָיָה רַבִּי מֵאִיר: תַּחַשׁ שֶׁהָיָה בִּימֵי מֹשֶׁה בְּרִיָּה בִּפְנֵי עַצְמָהּ הָיָה, וְלֹא הִכְרִיעוּ בּוֹ חֲכָמִים אִם מִין חַיָּה הוּא, אִם מִין בְּהֵמָה הוּא. וְקֶרֶן אַחַת הָיְתָה לוֹ בְּמִצְחוֹ, וּלְפִי שָׁעָה נִזְדַּמֵּן לוֹ לְמֹשֶׁה וְעָשָׂה מִמֶּנּוּ מִשְׁכָּן וְנִגְנַז. מִדְּקָאָמַר קֶרֶן אַחַת הָיְתָה לוֹ בְּמִצְחוֹ, שְׁמַע מִינַּהּ טָהוֹר הָיָה, דְּאָמַר רַב יְהוּדָה: שׁוֹר שֶׁהִקְרִיב אָדָם הָרִאשׁוֹן קֶרֶן אַחַת הָיְתָה לוֹ בְּמִצְחוֹ, שֶׁנֶּאֱמַר: ״וְתִיטַב לַיקוק מִשּׁוֹר פָּר מַקְרִין מַפְרִיס״. ״מַקְרִין״ תַּרְתֵּי מַשְׁמַע! אָמַר רַב נַחְמָן בַּר יִצְחָק — ״מַקְרָן״ כְּתִיב. וְלִיפְשׁוֹט מִינֵּיהּ דְּמִין בְּהֵמָה הוּא? כֵּיוָן דְּאִיכָּא ״קֶרֶשׁ״ דְּמִין חַיָּה הוּא וְלֵית לֵיהּ אֶלָּא חֲדָא קֶרֶן — אִיכָּא לְמֵימַר מִין חַיָּה הוּא.
The Gemara asks: What is the halakhic conclusion reached about this matter of the taḥash that existed in the days of Moses? Rabbi Ela said that Rabbi Shimon ben Lakish said that Rabbi Meir used to say: The taḥash that existed in the days of Moses was a creature unto itself, and the Sages did not determine whether it was a type of undomesticated animal or a type of domesticated animal. And it had a single horn on its forehead, and this taḥashhappened to come to Moses for the moment while the Tabernacle was being built, and he made the covering for the Tabernacle from it. And from then on, the taḥashwas suppressed and is no longer found.
The Gemara comments: From the fact that it is said that the taḥashhad a single horn on its forehead, conclude from this that it was kosher, as Rav Yehuda said in a similar vein: The ox that Adam, the first man, sacrificed as a thanks-offering for his life being spared, had a single horn on its forehead, as it is stated: “And it shall please the Lord better than a horned [makrin] and hooved ox” (Psalms 69:32). The word makrin means one with a horn. The Gemara asks: On the contrary, makrin indicates that it has two horns. Rav Naḥman bar Yitzḥak said: Despite the fact that it is vocalized in the plural, it is written mikeren without the letter yod to indicate that it had only a single horn. The Gemara asks: If so, let us resolve from the same baraita that just as it was derived from the ox of Adam, the first man, that an animal with one horn is kosher, derive that an animal with one horn is a type of domesticated animal. The Gemara answers: Since there is the keresh which is a type of undomesticated animal, and it has only a single horn, it is also possible to say that the taḥash is a type of undomesticated animal. This dilemma was not resolved.
The Rabbis of Midrash similarly discuss the origin of "sealskins" (i.e., "dolphin skins"):
וְזֹאת הַתְּרוּמָה וְגוֹ'. וְעֹרֹת אֵילִם מְאָדָּמִים וְעֹרֹת תְּחָשִׁים. רַבִּי יְהוּדָה וְרַבִּי נֶחְמְיָה. רַבִּי יְהוּדָה אוֹמֵר: חַיָּה טְהוֹרָה גְּדוֹלָה הָיְתָה בַּמִּדְבָּר וְקֶרֶן אַחַת הָיָה לָהּ בְּמִצְחָהּ, וּבְעוֹרָהּ שִׁשָּׁה גְּוָנִים, וְנָטְלוּ אוֹתָהּ וְעָשׂוּ מִמֶּנָּה יְרִיעוֹת. וְרַבִּי נְחֶמְיָה אוֹמֵר: מַעֲשֵׂה נִסִּים הָיְתָה, וּלְשָׁעָה שֶׁנִּבְרֵאת, בָּהּ בַּשָּׁנָה נִגְנְזָה. וְעֹרֹת תְּחָשִׁים, לָמָּה? דִּכְתִיב: אֹרֶךְ הַיְרִיעָה הָאַחַת שְׁלֹשִים בָּאַמָּה. מִי מֵבִיא לְךָ יְרִיעָה שֶׁל שְׁלֹשִׁים אַמָּה. אֶלָּא מַעֲשֵׂה נֵס, לְשָׁעָה שֶׁנִּבְרֵאת נִגְנְזָה.
This is the offering … and rams’ skins dyed red, and sealskins (Exod. 25:3). R. Judah and R. Nehemiah discussed this verse. R. Judah said: It was a large pure animal, with a single horn in its forehead and a skin of six different colors that roamed the desert. They captured one of them and from its skin made a covering for the ark. R. Nehemiah contended that it was a miraculous creature He created for that precise moment, and that it disappeared immediately thereafter from earth. Why is it called orot tahashim (“sealskins,” lit. “skins of tahashim”)? Because the verse states: The length of each curtain shall be thirty cubits (Exod. 26:8). What known animal could supply enough skin for a curtain of thirty cubits? It must, indeed, have been a miraculous creation, which disappeared (immediately after it was created).
Citing the above sources, Rashi (11th Century) describes "dolphin skins" as coming from a wild beast that existed only at the time of the Tabernacle:
תחשים. מִין חַיָּה, וְלֹא הָיְתָה אֶלָּא לְשָׁעָה, וְהַרְבֵּה גְּוָנִים הָיוּ לָהּ, לְכָךְ מְתֻרְגָּם סַסְגּוֹנָא שֶׁשָּׂשׂ וּמִתְפָּאֵר בִּגְוָנִין שֶׁלּוֹ (שבת כ"ח):
תחשים TACHASH was a kind of wild beast. It existed only at that time (when Israel built the Tabernacle). It was multi-coloured and therefore it is translated in the Targum by ססגונה, and it is so translated because it delights (שָׂשׂ) and prides itself in its colours (גונא) (Shabbat 28; Midrash Tanchuma, Terumah 6).
Ibn Ezra (12th Century) identifies "sealskins" as coming from an animal known at the time.
תחשים. מין חיה היתה ידועה בימים ההם. כי כן כתוב ואנעלך תחש. והנה כבר היה נודע:
AND SEALSKINS. Techashim (seals) refers to a type of animal that was known then, as it is written, va-ena’alekh tachash (and shod thee with sealskin) (Ezek. 16:10). It is thus clear that it was already known.
While the material nature of "dolphin skins" (or "sealskins") remains a mystery, its significance may be ascertainable from the Hebrew.
In the Torah, "dolphin skin(s)" is always associated with the Tabernacle or Tent of Meeting, mentioned in Parashiyot Terumah, Vayakhel, Pekudei, and Bamidbar:
(ה) וְעֹרֹ֨ת אֵילִ֧ם מְאׇדָּמִ֛ים וְעֹרֹ֥ת תְּחָשִׁ֖ים וַעֲצֵ֥י שִׁטִּֽים׃
(5) tanned ram skins, dolphin skins, and acacia wood;
(יד) וְעָשִׂ֤יתָ מִכְסֶה֙ לָאֹ֔הֶל עֹרֹ֥ת אֵילִ֖ם מְאׇדָּמִ֑ים וּמִכְסֵ֛ה עֹרֹ֥ת תְּחָשִׁ֖ים מִלְמָֽעְלָה׃ {פ}
(14) And make for the tent a covering of tanned ram skins, and a covering of dolphin skins above.
(ז) וְעֹרֹ֨ת אֵילִ֧ם מְאׇדָּמִ֛ים וְעֹרֹ֥ת תְּחָשִׁ֖ים וַעֲצֵ֥י שִׁטִּֽים׃
(7) tanned ram skins, dolphin skins, and acacia wood;
(כג) וְכׇל־אִ֞ישׁ אֲשֶׁר־נִמְצָ֣א אִתּ֗וֹ תְּכֵ֧לֶת וְאַרְגָּמָ֛ן וְתוֹלַ֥עַת שָׁנִ֖י וְשֵׁ֣שׁ וְעִזִּ֑ים וְעֹרֹ֨ת אֵילִ֧ם מְאׇדָּמִ֛ים וְעֹרֹ֥ת תְּחָשִׁ֖ים הֵבִֽיאוּ׃
(23) And everyone who possessed blue, purple, and crimson yarns, fine linen, goats’ hair, tanned ram skins, and dolphin skins, brought them;
(יט) וַיַּ֤עַשׂ מִכְסֶה֙ לָאֹ֔הֶל עֹרֹ֥ת אֵילִ֖ם מְאׇדָּמִ֑ים וּמִכְסֵ֛ה עֹרֹ֥ת תְּחָשִׁ֖ים מִלְמָֽעְלָה׃ {ס}
(19) And they made a covering of tanned ram skins for the tent, and a covering of dolphin skins above.
(לד) וְאֶת־מִכְסֵ֞ה עוֹרֹ֤ת הָֽאֵילִם֙ הַמְאׇדָּמִ֔ים וְאֶת־מִכְסֵ֖ה עֹרֹ֣ת הַתְּחָשִׁ֑ים וְאֵ֖ת פָּרֹ֥כֶת הַמָּסָֽךְ׃
(34) the covering of tanned ram skins, the covering of dolphin skins, and the curtain for the screen;
(ו) וְנָתְנ֣וּ עָלָ֗יו כְּסוּי֙ ע֣וֹר תַּ֔חַשׁ וּפָרְשׂ֧וּ בֶֽגֶד־כְּלִ֛יל תְּכֵ֖לֶת מִלְמָ֑עְלָה וְשָׂמ֖וּ בַּדָּֽיו׃ (ז) וְעַ֣ל ׀ שֻׁלְחַ֣ן הַפָּנִ֗ים יִפְרְשׂוּ֮ בֶּ֣גֶד תְּכֵ֒לֶת֒ וְנָתְנ֣וּ עָ֠לָ֠יו אֶת־הַקְּעָרֹ֤ת וְאֶת־הַכַּפֹּת֙ וְאֶת־הַמְּנַקִּיֹּ֔ת וְאֵ֖ת קְשׂ֣וֹת הַנָּ֑סֶךְ וְלֶ֥חֶם הַתָּמִ֖יד עָלָ֥יו יִהְיֶֽה׃ (ח) וּפָרְשׂ֣וּ עֲלֵיהֶ֗ם בֶּ֚גֶד תּוֹלַ֣עַת שָׁנִ֔י וְכִסּ֣וּ אֹת֔וֹ בְּמִכְסֵ֖ה ע֣וֹר תָּ֑חַשׁ וְשָׂמ֖וּ אֶת־בַּדָּֽיו׃ (ט) וְלָקְח֣וּ ׀ בֶּ֣גֶד תְּכֵ֗לֶת וְכִסּ֞וּ אֶת־מְנֹרַ֤ת הַמָּאוֹר֙ וְאֶת־נֵ֣רֹתֶ֔יהָ וְאֶת־מַלְקָחֶ֖יהָ וְאֶת־מַחְתֹּתֶ֑יהָ וְאֵת֙ כׇּל־כְּלֵ֣י שַׁמְנָ֔הּ אֲשֶׁ֥ר יְשָׁרְתוּ־לָ֖הּ בָּהֶֽם׃ (י) וְנָתְנ֤וּ אֹתָהּ֙ וְאֶת־כׇּל־כֵּלֶ֔יהָ אֶל־מִכְסֵ֖ה ע֣וֹר תָּ֑חַשׁ וְנָתְנ֖וּ עַל־הַמּֽוֹט׃ (יא) וְעַ֣ל ׀ מִזְבַּ֣ח הַזָּהָ֗ב יִפְרְשׂוּ֙ בֶּ֣גֶד תְּכֵ֔לֶת וְכִסּ֣וּ אֹת֔וֹ בְּמִכְסֵ֖ה ע֣וֹר תָּ֑חַשׁ וְשָׂמ֖וּ אֶת־בַּדָּֽיו׃ (יב) וְלָקְחוּ֩ אֶת־כׇּל־כְּלֵ֨י הַשָּׁרֵ֜ת אֲשֶׁ֧ר יְשָֽׁרְתוּ־בָ֣ם בַּקֹּ֗דֶשׁ וְנָֽתְנוּ֙ אֶל־בֶּ֣גֶד תְּכֵ֔לֶת וְכִסּ֣וּ אוֹתָ֔ם בְּמִכְסֵ֖ה ע֣וֹר תָּ֑חַשׁ וְנָתְנ֖וּ עַל־הַמּֽוֹט׃ (יג) וְדִשְּׁנ֖וּ אֶת־הַמִּזְבֵּ֑חַ וּפָרְשׂ֣וּ עָלָ֔יו בֶּ֖גֶד אַרְגָּמָֽן׃ (יד) וְנָתְנ֣וּ עָ֠לָ֠יו אֶֽת־כׇּל־כֵּלָ֞יו אֲשֶׁ֣ר יְֽשָׁרְת֧וּ עָלָ֣יו בָּהֶ֗ם אֶת־הַמַּחְתֹּ֤ת אֶת־הַמִּזְלָגֹת֙ וְאֶת־הַיָּעִ֣ים וְאֶת־הַמִּזְרָקֹ֔ת כֹּ֖ל כְּלֵ֣י הַמִּזְבֵּ֑חַ וּפָרְשׂ֣וּ עָלָ֗יו כְּס֛וּי ע֥וֹר תַּ֖חַשׁ וְשָׂמ֥וּ בַדָּֽיו׃
(6) They shall lay a covering of dolphin skin over it and spread a cloth of pure blue on top; and they shall put its poles in place. (7) Over the table of display they shall spread a blue cloth; they shall place upon it the bowls, the ladles, the jars, and the libation jugs; and the regular bread shall rest upon it. (8) They shall spread over these a crimson cloth which they shall cover with a covering of dolphin skin; and they shall put the poles in place. (9) Then they shall take a blue cloth and cover the lampstand for lighting, with its lamps, its tongs, and its fire pans, as well as all the oil vessels that are used in its service. (10) They shall put it and all its furnishings into a covering of dolphin skin, which they shall then place on a carrying frame. (11) Next they shall spread a blue cloth over the altar of gold and cover it with a covering of dolphin skin; and they shall put its poles in place. (12) They shall take all the service vessels with which the service in the sanctuary is performed, put them into a blue cloth and cover them with a covering of dolphin skin, which they shall then place on a carrying frame. (13) They shall remove the ashes from the [copper] altar and spread a purple cloth over it. (14) Upon it they shall place all the vessels that are used in its service: the fire pans, the flesh hooks, the scrapers, and the basins—all the vessels of the altar—and over it they shall spread a covering of dolphin skin; and they shall put its poles in place.
(כה) וְנָ֨שְׂא֜וּ אֶת־יְרִיעֹ֤ת הַמִּשְׁכָּן֙ וְאֶת־אֹ֣הֶל מוֹעֵ֔ד מִכְסֵ֕הוּ וּמִכְסֵ֛ה הַתַּ֥חַשׁ אֲשֶׁר־עָלָ֖יו מִלְמָ֑עְלָה וְאֶ֨ת־מָסַ֔ךְ פֶּ֖תַח אֹ֥הֶל מוֹעֵֽד׃
(25) they shall carry the cloths of the Tabernacle, the Tent of Meeting with its covering, the covering of dolphin skin that is on top of it, and the screen for the entrance of the Tent of Meeting;
These occurrences of "dolphin skin(s)" are interesting in that they switch from plural (typically עֹרֹת תְּחָשִׁים) in Exodus to singular (typically עוֹר תָּחַשׁ) in Numbers. In the plural, עֹרֹת uses two cholam chaser ( ֺ) while in the singular, עוֹר uses a cholam malei (וֹ); in contrast, עוֹרֹת appears in Ex. 39:34 in the context of עוֹרֹת הָאֵילִם הַמְאׇדָּמִים. It is worth noting that the plural occurrences in Exodus relate to construction of the Tabernacle while the singular occurrences in Numbers relate to deconstruction of the Tabernacle with its Tent of Meeting for transport.
The full-singular (עוֹר תָּחַשׁ) occurrences in Numbers concern the "responsibility of the Kohathites in the Tent of Meeting: the most sacred objects":
(א) וַיְדַבֵּ֣ר יקוק אֶל־מֹשֶׁ֥ה וְאֶֽל־אַהֲרֹ֖ן לֵאמֹֽר׃ (ב) נָשֹׂ֗א אֶת־רֹאשׁ֙ בְּנֵ֣י קְהָ֔ת מִתּ֖וֹךְ בְּנֵ֣י לֵוִ֑י לְמִשְׁפְּחֹתָ֖ם לְבֵ֥ית אֲבֹתָֽם׃ (ג) מִבֶּ֨ן שְׁלֹשִׁ֤ים שָׁנָה֙ וָמַ֔עְלָה וְעַ֖ד בֶּן־חֲמִשִּׁ֣ים שָׁנָ֑ה כׇּל־בָּא֙ לַצָּבָ֔א לַעֲשׂ֥וֹת מְלָאכָ֖ה בְּאֹ֥הֶל מוֹעֵֽד׃ (ד) זֹ֛את עֲבֹדַ֥ת בְּנֵי־קְהָ֖ת בְּאֹ֣הֶל מוֹעֵ֑ד קֹ֖דֶשׁ הַקֳּדָשִֽׁים׃ (ה) וּבָ֨א אַהֲרֹ֤ן וּבָנָיו֙ בִּנְסֹ֣עַ הַֽמַּחֲנֶ֔ה וְהוֹרִ֕דוּ אֵ֖ת פָּרֹ֣כֶת הַמָּסָ֑ךְ וְכִ֨סּוּ־בָ֔הּ אֵ֖ת אֲרֹ֥ן הָעֵדֻֽת׃ (ו) וְנָתְנ֣וּ עָלָ֗יו כְּסוּי֙ ע֣וֹר תַּ֔חַשׁ וּפָרְשׂ֧וּ בֶֽגֶד־כְּלִ֛יל תְּכֵ֖לֶת מִלְמָ֑עְלָה וְשָׂמ֖וּ בַּדָּֽיו׃ (ז) וְעַ֣ל ׀ שֻׁלְחַ֣ן הַפָּנִ֗ים יִפְרְשׂוּ֮ בֶּ֣גֶד תְּכֵ֒לֶת֒ וְנָתְנ֣וּ עָ֠לָ֠יו אֶת־הַקְּעָרֹ֤ת וְאֶת־הַכַּפֹּת֙ וְאֶת־הַמְּנַקִּיֹּ֔ת וְאֵ֖ת קְשׂ֣וֹת הַנָּ֑סֶךְ וְלֶ֥חֶם הַתָּמִ֖יד עָלָ֥יו יִהְיֶֽה׃ (ח) וּפָרְשׂ֣וּ עֲלֵיהֶ֗ם בֶּ֚גֶד תּוֹלַ֣עַת שָׁנִ֔י וְכִסּ֣וּ אֹת֔וֹ בְּמִכְסֵ֖ה ע֣וֹר תָּ֑חַשׁ וְשָׂמ֖וּ אֶת־בַּדָּֽיו׃ (ט) וְלָקְח֣וּ ׀ בֶּ֣גֶד תְּכֵ֗לֶת וְכִסּ֞וּ אֶת־מְנֹרַ֤ת הַמָּאוֹר֙ וְאֶת־נֵ֣רֹתֶ֔יהָ וְאֶת־מַלְקָחֶ֖יהָ וְאֶת־מַחְתֹּתֶ֑יהָ וְאֵת֙ כׇּל־כְּלֵ֣י שַׁמְנָ֔הּ אֲשֶׁ֥ר יְשָׁרְתוּ־לָ֖הּ בָּהֶֽם׃ (י) וְנָתְנ֤וּ אֹתָהּ֙ וְאֶת־כׇּל־כֵּלֶ֔יהָ אֶל־מִכְסֵ֖ה ע֣וֹר תָּ֑חַשׁ וְנָתְנ֖וּ עַל־הַמּֽוֹט׃ (יא) וְעַ֣ל ׀ מִזְבַּ֣ח הַזָּהָ֗ב יִפְרְשׂוּ֙ בֶּ֣גֶד תְּכֵ֔לֶת וְכִסּ֣וּ אֹת֔וֹ בְּמִכְסֵ֖ה ע֣וֹר תָּ֑חַשׁ וְשָׂמ֖וּ אֶת־בַּדָּֽיו׃ (יב) וְלָקְחוּ֩ אֶת־כׇּל־כְּלֵ֨י הַשָּׁרֵ֜ת אֲשֶׁ֧ר יְשָֽׁרְתוּ־בָ֣ם בַּקֹּ֗דֶשׁ וְנָֽתְנוּ֙ אֶל־בֶּ֣גֶד תְּכֵ֔לֶת וְכִסּ֣וּ אוֹתָ֔ם בְּמִכְסֵ֖ה ע֣וֹר תָּ֑חַשׁ וְנָתְנ֖וּ עַל־הַמּֽוֹט׃ (יג) וְדִשְּׁנ֖וּ אֶת־הַמִּזְבֵּ֑חַ וּפָרְשׂ֣וּ עָלָ֔יו בֶּ֖גֶד אַרְגָּמָֽן׃ (יד) וְנָתְנ֣וּ עָ֠לָ֠יו אֶֽת־כׇּל־כֵּלָ֞יו אֲשֶׁ֣ר יְֽשָׁרְת֧וּ עָלָ֣יו בָּהֶ֗ם אֶת־הַמַּחְתֹּ֤ת אֶת־הַמִּזְלָגֹת֙ וְאֶת־הַיָּעִ֣ים וְאֶת־הַמִּזְרָקֹ֔ת כֹּ֖ל כְּלֵ֣י הַמִּזְבֵּ֑חַ וּפָרְשׂ֣וּ עָלָ֗יו כְּס֛וּי ע֥וֹר תַּ֖חַשׁ וְשָׂמ֥וּ בַדָּֽיו׃ (טו) וְכִלָּ֣ה אַֽהֲרֹן־וּ֠בָנָ֠יו לְכַסֹּ֨ת אֶת־הַקֹּ֜דֶשׁ וְאֶת־כׇּל־כְּלֵ֣י הַקֹּ֘דֶשׁ֮ בִּנְסֹ֣עַ הַֽמַּחֲנֶה֒ וְאַחֲרֵי־כֵ֗ן יָבֹ֤אוּ בְנֵי־קְהָת֙ לָשֵׂ֔את וְלֹֽא־יִגְּע֥וּ אֶל־הַקֹּ֖דֶשׁ וָמֵ֑תוּ אֵ֛לֶּה מַשָּׂ֥א בְנֵֽי־קְהָ֖ת בְּאֹ֥הֶל מוֹעֵֽד׃ (טז) וּפְקֻדַּ֞ת אֶלְעָזָ֣ר ׀ בֶּן־אַהֲרֹ֣ן הַכֹּהֵ֗ן שֶׁ֤מֶן הַמָּאוֹר֙ וּקְטֹ֣רֶת הַסַּמִּ֔ים וּמִנְחַ֥ת הַתָּמִ֖יד וְשֶׁ֣מֶן הַמִּשְׁחָ֑ה פְּקֻדַּ֗ת כׇּל־הַמִּשְׁכָּן֙ וְכׇל־אֲשֶׁר־בּ֔וֹ בְּקֹ֖דֶשׁ וּבְכֵלָֽיו׃ {פ} (יז) וַיְדַבֵּ֣ר יקוק אֶל־מֹשֶׁ֥ה וְאֶֽל־אַהֲרֹ֖ן לֵאמֹֽר׃ (יח) אַל־תַּכְרִ֕יתוּ אֶת־שֵׁ֖בֶט מִשְׁפְּחֹ֣ת הַקְּהָתִ֑י מִתּ֖וֹךְ הַלְוִיִּֽם׃ (יט) וְזֹ֣את ׀ עֲשׂ֣וּ לָהֶ֗ם וְחָיוּ֙ וְלֹ֣א יָמֻ֔תוּ בְּגִשְׁתָּ֖ם אֶת־קֹ֣דֶשׁ הַקֳּדָשִׁ֑ים אַהֲרֹ֤ן וּבָנָיו֙ יָבֹ֔אוּ וְשָׂמ֣וּ אוֹתָ֗ם אִ֥ישׁ אִ֛ישׁ עַל־עֲבֹדָת֖וֹ וְאֶל־מַשָּׂאֽוֹ׃ (כ) וְלֹא־יָבֹ֧אוּ לִרְא֛וֹת כְּבַלַּ֥ע אֶת־הַקֹּ֖דֶשׁ וָמֵֽתוּ׃ {פ}
(1)יקוק spoke to Moses and Aaron, saying: (2) Take a [separate] census of the Kohathites among the Levites, by the clans of their ancestral house, (3) from the age of thirty years up to the age of fifty, all who are subject to service, to perform tasks for the Tent of Meeting. (4) This is the responsibility of the Kohathites in the Tent of Meeting: the most sacred objects. (5) At the breaking of camp, Aaron and his sons shall go in and take down the screening curtain and cover the Ark of the Pact with it. (6) They shall lay a covering of dolphin skin over it and spread a cloth of pure blue on top; and they shall put its poles in place. (7) Over the table of display they shall spread a blue cloth; they shall place upon it the bowls, the ladles, the jars, and the libation jugs; and the regular bread shall rest upon it. (8) They shall spread over these a crimson cloth which they shall cover with a covering of dolphin skin; and they shall put the poles in place. (9) Then they shall take a blue cloth and cover the lampstand for lighting, with its lamps, its tongs, and its fire pans, as well as all the oil vessels that are used in its service. (10) They shall put it and all its furnishings into a covering of dolphin skin, which they shall then place on a carrying frame. (11) Next they shall spread a blue cloth over the altar of gold and cover it with a covering of dolphin skin; and they shall put its poles in place. (12) They shall take all the service vessels with which the service in the sanctuary is performed, put them into a blue cloth and cover them with a covering of dolphin skin, which they shall then place on a carrying frame. (13) They shall remove the ashes from the [copper] altar and spread a purple cloth over it. (14) Upon it they shall place all the vessels that are used in its service: the fire pans, the flesh hooks, the scrapers, and the basins—all the vessels of the altar—and over it they shall spread a covering of dolphin skin; and they shall put its poles in place. (15) When Aaron and his sons have finished covering the sacred objects and all the furnishings of the sacred objects at the breaking of camp, only then shall the Kohathites come and lift them, so that they do not come in contact with the sacred objects and die. These things in the Tent of Meeting shall be the porterage of the Kohathites. (16) Responsibility shall rest with Eleazar son of Aaron the priest for the lighting oil, the aromatic incense, the regular meal offering, and the anointing oil—responsibility for the whole Tabernacle and for everything consecrated that is in it or in its vessels. (17)יקוק spoke to Moses and Aaron, saying: (18) Do not let the group of Kohathite clans be cut off from the Levites. (19) Do this with them, that they may live and not die when they approach the most sacred objects: let Aaron and his sons go in and assign each of them to his duties and to his porterage. (20) But let not [the Kohathites] go inside and witness the dismantling of the sanctuary, lest they die.
Aaron, the High Priest, and his sons are responsible for preparing for transport the most-sacred objects in the Tent of Meeting, which is part of the Tabernacle. The preparation steps are detailed and mention in close succession "dolphin skin" (עוֹר תָּחַשׁ) six times. Dolphin skin is mostly used as the final covering before the transport poles are put in place. It seems that the dolphin skin serves as a protective barrier to prevent the Kohathites from touching the most-sacred objects and dying as a consequence.
The strong association here between Aaron, the High Priest, and "dolphin skin" is no accident. Between the first mention of "dolphin skins" in Parashat Terumah and the next in Parashat Vayakhel, the incident of the Golden Calf occurs with Aaron in its midst:
(א) וַיַּ֣רְא הָעָ֔ם כִּֽי־בֹשֵׁ֥שׁ מֹשֶׁ֖ה לָרֶ֣דֶת מִן־הָהָ֑ר וַיִּקָּהֵ֨ל הָעָ֜ם עַֽל־אַהֲרֹ֗ן וַיֹּאמְר֤וּ אֵלָיו֙ ק֣וּם ׀ עֲשֵׂה־לָ֣נוּ אֱלֹקִ֗ים אֲשֶׁ֤ר יֵֽלְכוּ֙ לְפָנֵ֔ינוּ כִּי־זֶ֣ה ׀ מֹשֶׁ֣ה הָאִ֗ישׁ אֲשֶׁ֤ר הֶֽעֱלָ֙נוּ֙ מֵאֶ֣רֶץ מִצְרַ֔יִם לֹ֥א יָדַ֖עְנוּ מֶה־הָ֥יָה לֽוֹ׃ (ב) וַיֹּ֤אמֶר אֲלֵהֶם֙ אַהֲרֹ֔ן פָּֽרְקוּ֙ נִזְמֵ֣י הַזָּהָ֔ב אֲשֶׁר֙ בְּאׇזְנֵ֣י נְשֵׁיכֶ֔ם בְּנֵיכֶ֖ם וּבְנֹתֵיכֶ֑ם וְהָבִ֖יאוּ אֵלָֽי׃ (ג) וַיִּתְפָּֽרְקוּ֙ כׇּל־הָעָ֔ם אֶת־נִזְמֵ֥י הַזָּהָ֖ב אֲשֶׁ֣ר בְּאׇזְנֵיהֶ֑ם וַיָּבִ֖יאוּ אֶֽל־אַהֲרֹֽן׃ (ד)וַיִּקַּ֣ח מִיָּדָ֗ם וַיָּ֤צַר אֹתוֹ֙ בַּחֶ֔רֶט וַֽיַּעֲשֵׂ֖הוּ עֵ֣גֶל מַסֵּכָ֑ה וַיֹּ֣אמְר֔וּ אֵ֤לֶּה אֱלֹקֶ֙יךָ֙ יִשְׂרָאֵ֔ל אֲשֶׁ֥ר הֶעֱל֖וּךָ מֵאֶ֥רֶץ מִצְרָֽיִם׃(ה) וַיַּ֣רְא אַהֲרֹ֔ן וַיִּ֥בֶן מִזְבֵּ֖חַ לְפָנָ֑יו וַיִּקְרָ֤א אַֽהֲרֹן֙ וַיֹּאמַ֔ר חַ֥ג לַיקוק מָחָֽר׃ (ו) וַיַּשְׁכִּ֙ימוּ֙ מִֽמׇּחֳרָ֔ת וַיַּעֲל֣וּ עֹלֹ֔ת וַיַּגִּ֖שׁוּ שְׁלָמִ֑ים וַיֵּ֤שֶׁב הָעָם֙ לֶֽאֱכֹ֣ל וְשָׁת֔וֹ וַיָּקֻ֖מוּ לְצַחֵֽק׃ {פ} (ז)וַיְדַבֵּ֥ר יקוק אֶל־מֹשֶׁ֑ה לֶךְ־רֵ֕ד כִּ֚י שִׁחֵ֣ת עַמְּךָ֔ אֲשֶׁ֥ר הֶעֱלֵ֖יתָ מֵאֶ֥רֶץ מִצְרָֽיִם׃ (ח) סָ֣רוּ מַהֵ֗ר מִן־הַדֶּ֙רֶךְ֙ אֲשֶׁ֣ר צִוִּיתִ֔ם עָשׂ֣וּ לָהֶ֔ם עֵ֖גֶל מַסֵּכָ֑ה וַיִּשְׁתַּֽחֲווּ־לוֹ֙ וַיִּזְבְּחוּ־ל֔וֹ וַיֹּ֣אמְר֔וּ אֵ֤לֶּה אֱלֹקֶ֙יךָ֙ יִשְׂרָאֵ֔ל אֲשֶׁ֥ר הֶֽעֱל֖וּךָ מֵאֶ֥רֶץ מִצְרָֽיִם׃ (ט) וַיֹּ֥אמֶר יקוק אֶל־מֹשֶׁ֑ה רָאִ֙יתִי֙ אֶת־הָעָ֣ם הַזֶּ֔ה וְהִנֵּ֥ה עַם־קְשֵׁה־עֹ֖רֶף הֽוּא׃ (י) וְעַתָּה֙ הַנִּ֣יחָה לִּ֔י וְיִֽחַר־אַפִּ֥י בָהֶ֖ם וַאֲכַלֵּ֑ם וְאֶֽעֱשֶׂ֥ה אוֹתְךָ֖ לְג֥וֹי גָּדֽוֹל׃
(1) When the people saw that Moses was so long in coming down from the mountain, the people gathered against Aaron and said to him, “Come, make us a god who shall go before us, for that fellow Moses—the man who brought us from the land of Egypt—we do not know what has happened to him.” (2) Aaron said to them, “[You men,] take off the gold rings that are on the ears of your wives, your sons, and your daughters, and bring them to me.” (3) And all the people took off the gold rings that were in their ears and brought them to Aaron. (4)This he took from them and cast in a mold, and made it into a molten calf. And they exclaimed, “This is your god, O Israel, who brought you out of the land of Egypt!”(5) When Aaron saw this, he built an altar before it; and Aaron announced: “Tomorrow shall be a festival of יקוק!”(6) Early next day, the people offered up burnt offerings and brought sacrifices of well-being; they sat down to eat and drink, and then rose to dance. (7)יקוק spoke to Moses, “Hurry down, for your people, whom you brought out of the land of Egypt, have acted basely.(8) They have been quick to turn aside from the way that I enjoined upon them. They have made themselves a molten calf and bowed low to it and sacrificed to it, saying: ‘This is your god, O Israel, who brought you out of the land of Egypt!’” (9)יקוק further said to Moses, “I see that this is a stiffnecked people. (10) Now, let Me be, that My anger may blaze forth against them and that I may destroy them, and make of you a great nation.”
Soon after, Moses confronts Aaron about the incident of the Golden Calf:
(יט) וַֽיְהִ֗י כַּאֲשֶׁ֤ר קָרַב֙ אֶל־הַֽמַּחֲנֶ֔ה וַיַּ֥רְא אֶת־הָעֵ֖גֶל וּמְחֹלֹ֑ת וַיִּֽחַר־אַ֣ף מֹשֶׁ֗ה וַיַּשְׁלֵ֤ךְ מִיָּדָו֙ אֶת־הַלֻּחֹ֔ת וַיְשַׁבֵּ֥ר אֹתָ֖ם תַּ֥חַת הָהָֽר׃ (כ) וַיִּקַּ֞ח אֶת־הָעֵ֨גֶל אֲשֶׁ֤ר עָשׂוּ֙ וַיִּשְׂרֹ֣ף בָּאֵ֔שׁ וַיִּטְחַ֖ן עַ֣ד אֲשֶׁר־דָּ֑ק וַיִּ֙זֶר֙ עַל־פְּנֵ֣י הַמַּ֔יִם וַיַּ֖שְׁקְ אֶת־בְּנֵ֥י יִשְׂרָאֵֽל׃ (כא) וַיֹּ֤אמֶר מֹשֶׁה֙ אֶֽל־אַהֲרֹ֔ן מֶֽה־עָשָׂ֥ה לְךָ֖ הָעָ֣ם הַזֶּ֑ה כִּֽי־הֵבֵ֥אתָ עָלָ֖יו חֲטָאָ֥ה גְדֹלָֽה׃ (כב)וַיֹּ֣אמֶר אַהֲרֹ֔ן אַל־יִ֥חַר אַ֖ף אֲדֹנִ֑י אַתָּה֙ יָדַ֣עְתָּ אֶת־הָעָ֔ם כִּ֥י בְרָ֖ע הֽוּא׃ (כג) וַיֹּ֣אמְרוּ לִ֔י עֲשֵׂה־לָ֣נוּ אֱלֹקִ֔ים אֲשֶׁ֥ר יֵלְכ֖וּ לְפָנֵ֑ינוּ כִּי־זֶ֣ה ׀ מֹשֶׁ֣ה הָאִ֗ישׁ אֲשֶׁ֤ר הֶֽעֱלָ֙נוּ֙ מֵאֶ֣רֶץ מִצְרַ֔יִם לֹ֥א יָדַ֖עְנוּ מֶה־הָ֥יָה לֽוֹ׃ (כד) וָאֹמַ֤ר לָהֶם֙ לְמִ֣י זָהָ֔ב הִתְפָּרָ֖קוּ וַיִּתְּנוּ־לִ֑י וָאַשְׁלִכֵ֣הוּ בָאֵ֔שׁ וַיֵּצֵ֖א הָעֵ֥גֶל הַזֶּֽה׃
(19) As soon as Moses came near the camp and saw the calf and the dancing, he became enraged; and he hurled the tablets from his hands and shattered them at the foot of the mountain. (20) He took the calf that they had made and burned it; he ground it to powder and strewed it upon the water and so made the Israelites drink it. (21) Moses said to Aaron, “What did this people do to you that you have brought such great sin upon them?” (22)Aaron said, “Let not my lord be enraged. You know that this people is bent on evil.(23) They said to me, ‘Make us a god to lead us; for that fellow Moses—the man who brought us from the land of Egypt—we do not know what has happened to him.’ (24) So I said to them, ‘Whoever has gold, take it off!’ They gave it to me and I hurled it into the fire and out came this calf!”
From a textual perspective, this incident with its aftermath possesses two interesting correspondences with the responsibility of Aaron and his sons concerning the most-sacred objects in the Tent of Meeting. First, Aaron makes for the people a molten calf (עֵגֶל מַסֵּכָה), but later in deconstructing the Tent of Meeting for the people, he places a covering of dolphin skin (מִכְסֵה עוֹר תָּחַשׁ) over the most-sacred objects to protect them. These two phrases are somewhat mirror images: מִכְסֵה עוֹר תָּחַשׁ vs. עֵגֶל מַסֵּכָה. Second, God tells Moses that Moses's ("your") people are acting basely (שִׁחֵת עַמְּךָ) and that He wants to destroy them, arguably because the people acted wickedly. In explaining to Moses what happened, Aaron notes that the people are "bent on evil" (בְרָע).
God's desire for destruction of the people seems very similar to a verse among the curses in Parashat Ki Tavo:
(כ) יְשַׁלַּ֣ח יקוק ׀ בְּ֠ךָ֠ אֶת־הַמְּאֵרָ֤ה אֶת־הַמְּהוּמָה֙ וְאֶת־הַמִּגְעֶ֔רֶת בְּכׇל־מִשְׁלַ֥ח יָדְךָ֖ אֲשֶׁ֣ר תַּעֲשֶׂ֑ה עַ֣ד הִשָּׁמֶדְךָ֤ וְעַד־אֲבׇדְךָ֙ מַהֵ֔ר מִפְּנֵ֛י רֹ֥עַ מַֽעֲלָלֶ֖יךָ אֲשֶׁ֥ר עֲזַבְתָּֽנִי׃
(20)יקוק will let loose against you calamity, panic, and frustration in all the enterprises you undertake, so that you shall soon be utterly wiped out because of your evildoing in forsaking Me.
There is correspondence between בְרָע (bent on evil) and רֹעַ (evildoing), which share the same root רע.
Aaron's role in the incident (reluctant in my view; see Rashi) also recalls, in a more literal sense, the negative commandment in Parashat Mishpatim:
(ב)לֹֽא־תִהְיֶ֥ה אַחֲרֵֽי־רַבִּ֖ים לְרָעֹ֑ת וְלֹא־תַעֲנֶ֣ה עַל־רִ֗ב לִנְטֹ֛ת אַחֲרֵ֥י רַבִּ֖ים לְהַטֹּֽת׃
(2)You shall neither side with the mighty to do wrong—you shall not give perverse testimony in a dispute so as to pervert it in favor of the mighty—
Taken literally, this negative commandment could mean to not follow, or be swayed by, the crowd to do evil. This seems to happen to Aaron, even if he is intending to stall for time to allow Moses to return before he completes the Golden Calf and the people worship it.
These two other verses possess important words based on רֹעַ :רע (evildoing); and לְרָעֹת (to do wrong). Each of these words occurs only once in the Torah.
The responsibility of Aaron and his sons includes their placement of "dolphin skin" (עוֹר תָּחַשׁ) over the most-sacred objects. Spelling עוֹר תָּחַשׁ in reverse yields שִׁחֵת רוֹעַ (vowels aside). As two separate words, שִׁחֵת means "corrupt" (perhaps self-corrupt), and רוֹעַ means "evildoing", with רוֹעַ as the equivalent to רֹעַ. These words are arguably references to the men's (if not people's) behavior in incident of the Golden Calf, in which Aaron is involved.
The conclusion here is that עוֹר תָּחַשׁ ("dolphin skin") is a subtle reminder to Aaron and his kin of the incident of the Golden Calf in their responsibilities for properly deconstructing for transport the Tabernacle with its Tent of Meeting. עוֹר תָּחַשׁ might even be a subtle warning to Aaron and his kin, similar to the warning in the aftermath of the rebellion of Korach against Moses and Aaron (interestingly enough):
(א) וַיְדַבֵּ֥ר יקוק אֶל־מֹשֶׁ֥ה לֵּאמֹֽר׃ (ב) אֱמֹ֨ר אֶל־אֶלְעָזָ֜ר בֶּן־אַהֲרֹ֣ן הַכֹּהֵ֗ן וְיָרֵ֤ם אֶת־הַמַּחְתֹּת֙ מִבֵּ֣ין הַשְּׂרֵפָ֔ה וְאֶת־הָאֵ֖שׁ זְרֵה־הָ֑לְאָה כִּ֖י קָדֵֽשׁוּ׃ (ג) אֵ֡ת מַחְתּוֹת֩ הַֽחַטָּאִ֨ים הָאֵ֜לֶּה בְּנַפְשֹׁתָ֗ם וְעָשׂ֨וּ אֹתָ֜ם רִקֻּעֵ֤י פַחִים֙ צִפּ֣וּי לַמִּזְבֵּ֔חַ כִּֽי־הִקְרִיבֻ֥ם לִפְנֵֽי־יקוק וַיִּקְדָּ֑שׁוּ וְיִֽהְי֥וּ לְא֖וֹת לִבְנֵ֥י יִשְׂרָאֵֽל׃ (ד) וַיִּקַּ֞ח אֶלְעָזָ֣ר הַכֹּהֵ֗ן אֵ֚ת מַחְתּ֣וֹת הַנְּחֹ֔שֶׁת אֲשֶׁ֥ר הִקְרִ֖יבוּ הַשְּׂרֻפִ֑ים וַֽיְרַקְּע֖וּם צִפּ֥וּי לַמִּזְבֵּֽחַ׃ (ה) זִכָּר֞וֹן לִבְנֵ֣י יִשְׂרָאֵ֗ל לְ֠מַ֠עַן אֲשֶׁ֨ר לֹֽא־יִקְרַ֜ב אִ֣ישׁ זָ֗ר אֲ֠שֶׁ֠ר לֹ֣א מִזֶּ֤רַע אַהֲרֹן֙ ה֔וּא לְהַקְטִ֥יר קְטֹ֖רֶת לִפְנֵ֣י יקוק וְלֹֽא־יִהְיֶ֤ה כְקֹ֙רַח֙ וְכַ֣עֲדָת֔וֹ כַּאֲשֶׁ֨ר דִּבֶּ֧ר יקוק בְּיַד־מֹשֶׁ֖ה לֽוֹ׃ {פ}
(1) יקוק spoke to Moses, saying: (2) Order Eleazar son of Aaron the priest to remove the fire pans—for they have become sacred—from among the charred remains; and scatter the coals abroad. (3) [Remove] the fire pans of those who have sinned at the cost of their lives, and let them be made into hammered sheets as plating for the altar—for once they have been used for offering to יקוק, they have become sacred—and let them serve as a warning to the people of Israel. (4) Eleazar the priest took the copper fire pans which had been used for offering by those who died in the fire; and they were hammered into plating for the altar, (5) as יקוק had ordered him through Moses. It was to be a reminder to the Israelites, so that no outsider—one not of Aaron’s offspring—should presume to offer incense before יקוק and suffer the fate of Korah and his band.
In both cases, something connected to evil behavior of Israelites becomes closely associated with the most-sacred objects. Aaron is involved in both.