Pure agency in the avodah

בענין שאמחז"ל על נדב ואביהוא שתויי יין נכנסו למקדש.

Regarding what Chazal said about Nadav and Avihu, that they entered the Mikdash having drunk wine (shesuyei yayin).

The Sefas Emes addresses the teaching of Chazal that Aharon's sons erred by entering the Sanctuary after drinking wine, and seeks to understand it in a deeper, more sympathetic light.

גם לפי פשוטו חלילה לומר שהיו מזלזלין ח"ו בעבודה.

Even according to the plain meaning, Heaven forbid to say that they were treating the avodah with disrespect, G-d forbid.

One cannot imagine that such great tzaddikim were being careless or irreverent in the service; their intention must have been entirely for the sake of Heaven.

רק כענין שמצינו אגברי' חמרא לדרדקא כי היכי דלימרו מילי.

Rather, it is like the matter we find, that they would give wine to the young children so that they would say their lessons (Bava Basra 22a).

Wine can serve a holy purpose — as when a little wine was given to schoolchildren to loosen them up and encourage them to recite their learning; Nadav and Avihu sought a similar elevation in their avodah.

ואיתא חמרי פקחין כו'. שהיין מעורר הלב כמ"ש ותירוש ינובב בתולות.

And it is brought, "wine makes [one] sharp," etc., for wine arouses the heart, as it is written, "and new wine (tirosh) shall make the maidens flourish (yenovev)" (Zechariah 9:17).

Wine has the power to awaken and stir the heart, opening it to inspiration; Nadav and Avihu intended to use this to ignite greater fervor in their service of Hashem.

אך הכהן שהוא שלוחו של מקום לא הי' רשאי להוסיף שום כח והתפעלות מצידו.

However, the Kohen, who is the agent (shaliach) of the Omnipresent, was not permitted to add any power or arousal (hispa'alus) of his own.

Herein lies their mistake: a Kohen acts purely as Hashem's emissary, and as a shaliach he may not introduce any self-generated excitement or initiative into the avodah; even holy enthusiasm of one's own is out of place.

וזה נקרא אשר לא צוה אותם שהי' צריך להיות כל העבודה רק בשליחות המקום ב"ה.

And this is what is called "which He had not commanded them" (Vayikra 10:1), for all the avodah needed to be solely in the shlichus (agency) of the Omnipresent, blessed be He.

The "strange fire which He had not commanded" was precisely this added, self-originated arousal; the entire service must flow only from Hashem's command, with the Kohen as a pure conduit and nothing added from himself.

והקב"ה מדקדק עם הצדיקים כחוט השערה:

And Hashem is exacting with the tzaddikim to a hair's breadth (k'chut ha'sa'arah).

Because they stood on so lofty a level, even this subtle deviation — adding their own inspiration where only pure shlichus was called for — was held to account, for Hashem judges the righteous with exacting precision.

Summary: The Sefas Emes refuses to read Nadav and Avihu's "wine" as disrespect. On the contrary, they sought to use wine's power to arouse the heart to greater fervor in their avodah, as we find wine used to inspire children to learn. Their subtle error was that a Kohen is purely Hashem's shaliach and may add no self-generated arousal of his own; the entire service must flow only from Divine command — the "fire which He had not commanded." Because Hashem is exacting with the righteous to a hair's breadth, even this refined deviation was called to account.