Sourcesheet containing texts referenced in the Sukkot podcast by Zvi Hirschfield, Sefi Kraut, and Susan Yammer.
Sources referenced by Susan Yammer
(ד) ועוד יש בארבעה מינין אלו ענין אחר, שהם דומים לאברים שבאדם היקרים (עי' מדרש רבה ויקרא פ' ל' ומדרש תנחומא אמור אות יט). שהאתרוג דומה ללב, שהוא משכן השכל, לרמז שיעבד בוראו בשכלו, והלולב דומה לשדרה שהיא העקר שבאדם לרמז שיישיר כל גופו. לעבודתו ברוך הוא, וההדס דומה לעינים, לרמוז שלא יתור אחר עיניו ביום שמחת לבו, והערבה דומה לשפתים, שבהן יגמר האדם כל מעשהו בדבור, לרמז שישים רסן בפיו ויכון דבריו ויירא מהשם יתברך אף בעת השמחה.
(4) And there is also another matter with these four things - that they are similar to precious limbs in a man (see Vayikra Rabbah 30:14; Midrash Tanchuma, Emor 19): As the citron is similar to the heart, which is the dwelling place of the intellect, to hint that he should serve His creator with his intellect; the lulav is similar to the backbone, which is the essence of a person, to hint that he should straighten himself completely for His service, blessed be He; the myrtle [leaves are] similar to the eyes, to hint that he should not stray after his eyes 'on the day of the rejoicing of his heart'; and the willow [leaves are] similar to the lips, with which a man completes all of his acts of speech, to hint that he should put a muzzle to his mouth, calibrate his words and fear God, may He be blessed, even at a time of joy.
Sources referenced by Penny Joel
(יג) רַבִּי יְהוּדָה בְּשֵׁם רַבִּי שִׁמְעוֹן בֶּן פָּזִי פָּתַח (משלי ד, י): שְׁמַע בְּנִי וְקַח אֲמָרָי, הַרְבֵּה קִיחוֹת צִוִּיתִי אֶתְכֶם בִּשְׁבִיל לְזַכּוֹתְכֶם, אָמַרְתִּי אֲלֵיכֶם (במדבר יט, ב): וְיִקְחוּ אֵלֶיךָ פָרָה אֲדֻמָּה תְּמִימָה, שֶׁמָּא בִּשְׁבִילִי, אֶלָּא בִּשְׁבִילְכֶם לְטַהֵר אֶתְכֶם, דִּכְתִיב (במדבר יט, יט): וְהִזָּה הַטָּהֹר עַל הַטָּמֵא. אָמַרְתִּי לָכֶם (שמות כה, ב): וְיִקְחוּ לִי תְּרוּמָה, בִּשְׁבִיל שֶׁאָדוּר בֵּינֵיכֶם. (שמות כה, ה): וְעָשׂוּ לִי מִקְדָּשׁ, כִּבְיָכוֹל אָמַר הַקָּדוֹשׁ בָּרוּךְ הוּא קְחוּ אוֹתִי וְאָדוּר בֵּינֵיכֶם, וְיִקְחוּ תְרוּמָה אֵינוֹ אוֹמֵר אֶלָּא וְיִקְחוּ לִי, אוֹתִי אַתֶּם לוֹקְחִים. אָמַרְתִּי לָכֶם (ויקרא כד, ב): וְיִקְחוּ אֵלֶיךָ שֶׁמֶן זַיִת זָךְ, וְכִי אוֹרָה שֶׁלָּכֶם אֲנִי צָרִיךְ, וְהָא כְתִיב (דניאל ב, כב): וּנְהוֹרָא עִמֵּהּ שְׁרֵא, אֶלָּא בִּשְׁבִיל לְזַכּוֹתְכֶם וּלְכַפֵּר עַל נַפְשׁוֹתֵיכֶם שֶׁמְּשׁוּלָה כַּנֵּר, שֶׁנֶּאֱמַר (משלי כ, כז): נֵר יי נִשְׁמַת אָדָם חֹפֵשׂ כָּל חַדְרֵי בָטֶן, וְעַכְשָׁיו שֶׁאָמַרְתִּי לָכֶם: וּלְקַחְתֶּם לָכֶם בַּיּוֹם הָרִאשׁוֹן, כְּדֵי לְזַכּוֹתְכֶם כְּדֵי שֶׁאוֹרִיד לָכֶם מָטָר, לְכָךְ משֶׁה מַזְהִיר לְיִשְׂרָאֵל: וּלְקַחְתֶּם לָכֶם בַּיּוֹם הָרִאשׁוֹן.
(13) Another explanation: "The fruit of a beautiful tree" - these are [referring to] Israel. Just like this citron (etrog), which has taste and has smell, so too Israel has among them people that have Torah and have good deeds. "The branches of a date palm" - these are [referring to] Israel. Just like this date, which has taste and has no smell, so too Israel has among them those that have Torah but do not have good deeds. "And a branch of a braided tree (a myrtle)" - these are [referring to] Israel. Just like this myrtle, which has smell and has no taste, so too Israel has among them those that have good deeds but do not have Torah. "And brook willows" - these are [referring to] Israel. Just like this willow, which has no smell and has no taste, so too Israel has among them people that have no Torah and have no good deeds. And what does the Holy One, blessed be He, do to them? To destroy them is impossible, but rather the Holy One, blessed be He, said "bind them all together [into] one grouping and these will atone for those." And if you will have done that, I will be elevated at that time. This is [the meaning of] what is written (Amos 9:6), "He Who built the upper chambers in the heavens" (indicating his elevation). And when is He elevated? When they make one grouping, as it is stated (Ibid.), "and established His grouping on the earth." Hence Moshe warned Israel, "And you shall take for yourselves on the first day."
Sources referenced by Zvi Hirschfield