אמר רבי יהודה משום רבי עקיבא … אמר הקדוש ברוך הוא: … ואמרו לפני בראש השנה מלכיות זכרונות ושופרות. מלכיות: כדי שתמליכוני עליכם. זכרונות: כדי שיעלה זכרוניכם לפני לטובה. ובמה? בשופר.

Rabbi Yehudah said an idea from Rabbi Aqiva …: The Holy One, blessed be He said, “… say before Me on Rosh haShanah, Malkhios, Zikhoronos and Shoferos.
“Malkhios: so that you shall make Me King over you;
“Zikhoronos: so that your memories shall come before Me;
“And with what? With a shofar.”

– Rosh haShanah 16a

(Sidenote: There is a dispute as to what this implies as to the nature of the obligation. Rashi holds that these berakhos are mandatory from the Torah, if said with / as part of shofar blowing. He says that Malkhios is the essence of the day, as we see in practice we combine it with the usual holiday blessing for the day. And the words “yom zikhron teru’ah — a day of memory of horn-blasts” obligates us in Zikhronos and Shoferos. The Ritva in general holds that asmachtos, usually translated as mnemonic devices, are actually hints from G-d that an idea is a good one, but not mandatory. Thus a law from an asmachta is one that was suggested by G-d but made obligatory by the Chakhamim. Here, the Ritva says it’s an asmachta — G-d said “say before me”, but it wasn’t made mandatory until the Chakhamim codified it.)

מתנ’: כל השופרות כשרים חוץ משל פרה מפני שהוא קרן אמר רבי יוסי והלא כל השופרות נקראו קרן שנאמר (יהושוע ו) במשוך בקרן היובל:

גמ’: … עולא אמר היינו טעמא דרבנן כדרב חסדא דאמר רב חסדא מפני מה אין כהן גדול נכנס בבגדי זהב לפני ולפנים לעבוד עבודה לפי שאין קטיגור נעשה סניגור

Mishnah: Every shofar is kosher except for that of a cow, because it’s called “qeren“. Rabbi Yosi said: but isn’t every shofar called “qeren“,  as it says “In the middle of the qeren of the yoveil” (Yehoshua 6)?

Gemara: Ula said: What is the reason for the Rabbanan [the unnamed first opinion in the mishnah]? [Because they rule] like Rav Chisda. For Rav Chisda said: Why doesn’t the kohein gadol wear the bigei zahav — [his full uniform, including] the golden clothes when lifnai velifnim — before Me and within [the Holy of Holies]? Because a prosecutor can not be turned into the defense attourney.

– Rosh haShanah 26a

Rav Dovid Lifshitz addressed these gemaras in his pre-Rosh haShanah shiur of 1989. (See here for an entry that opens with another thought from that talk.)

Notice that the kohein gadol did wear the full bigdei zahav the rest of Yom Kippur, including when doing the other parts of the service of the very same qorban! The notion that ein qeteigor naaseh saneigor, that the prosecution can’t become the defense, is not a law in atonement, it’s a law in lifnai velifnim.

What then does it mean when this rule applies to shofar? Rashi points out that the gemara is assuming a comparison — listening to the shofar is tantamount to entering the Holy of Holies, only performed by the kohein gadol on Yom Kippur!

To add something of my own to this thought, in the Sifra’s version of the thought Rabbi Yehudah repeated from R’ Aqiva, it concludes, “ובמה? בשופר של חרות — And with what? with a shofar of freedom.”  As Yeshaiah writes (27:12) “יג וְהָיָ֣ה ׀ בַּיּ֣וֹם הַה֗וּא יִתָּקַע֮ בְּשׁוֹפָ֣ר גָּדוֹל֒ וּבָ֗אוּ הָאֹֽבְדִים֙ בְּאֶ֣רֶץ אַשּׁ֔וּר וְהַנִּדָּחִ֖ים בְּאֶ֣רֶץ מִצְרָ֑יִם וְהִשְׁתַּֽחֲו֧וּ לַֽה’ בְּהַ֥ר הַקֹּ֖דֶשׁ בִּירֽוּשָׁלִָֽם׃ — And it will be on that day, he will blow a great shofar, and those lost in Ashur and those taken captive in Egypt will come and they will bow to Hashem on the holy mountain in Jerusalem.”

Similarly, the shofar‘s blow at the shemittah year declared the freedom of slaves. A slave who refuses his freedom, preferring to live under his master’s patronage, has his ear pierced.  The ear that heard “ki avadai heim — for they are My servants” (Vayiqra 25:42) should know “My servants — and not servants to my servants” (Bava Metzi’ah 10a).

Cheirus appears associated with the tablets, which rested in the ark in the center of the Holy of Holies.”חָר֖וּת עַל־הַלֻּחֹֽת׃’ “אל תקרי חָרוּת אלא חֵרוּת — ‘engraved (charus) on the tablets’ (Shemos 32:16) — don’t read ‘charus‘ (engraved), rather ‘cheirus‘ (freedom).” Note also how Yeshaiah associates the shofar’s call with coming to the Temple Mount. The shofar‘s call to freedom would seem to be an echo of the freedom engraved on the luchos.

Back to rebbe’s shiur…

Remember the feeling when you first came to the Kotel. The wall which Hashem promised us would stand until the end of time, whose persistence is testimony to our relationship with Him. And you reach the stones, the wall around the Temple Mount, and the feeling is overwhelming. Picture the emotions one would have being able to actually enter the courtyard. To be a kohein entering the Temple itself. To be the kohein gadol, after a week of preparation, now on the holiest day of the year busy with the holiest of service, to enter lifnai velifnim.

That’s Shofar.

How does one accept Hashem as Melekh, and remember our faults so that He remembers our potential? At that moment — “with the shofar.”

(Rebbe actually presented this thought before giving a source. After the students were entranced with the rebbe’s great chiddush, his passionate novellum, he asked one of them to read the Rashi and Tosafos. Had they known it was “just a Rashi”, they wouldn’t have listened the same.)