Smell as the sense of the soul

והנה כתיב והריחו ביראת ה' דרשו חז"ל על מלך המשיח דמורח ודאין.

Behold, it is written "and his delight (va-harícho) shall be in the fear of Hashem" (Yeshayahu 11:3), which Chazal expounded regarding Melech HaMashiach, who "smells and judges" (morach v'da'in).

The pasuk about Mashiach uses the root reiach (smell), and Chazal say Mashiach will judge by "smell" — by a refined spiritual sense rather than by ordinary sight and hearing.

ויצחק שהוא שרש היראה ראה מהריח מי שראוי לברכו.

And Yitzchak, who is the root of yirah (fear/awe), discerned by smell who was fit to bless.

Yitzchak embodies the middah of yiras Shomayim, and through this same elevated sense of smell — "the smell of my son is like the smell of a field" — he perceived who was truly worthy of the berachah.

והריח הוא מבחי' הנשמה כמ"ש חז"ל איזהו דבר שהנפש נהנה בו ולא הגוף זה הריח דכתיב כל הנשמה תהלל.

And smell is from the aspect of the neshamah, as Chazal said: what is something that the soul enjoys but the body does not — this is smell — as it is written, "Let every soul (neshamah) praise" (Tehillim 150:6).

Of all the senses, smell alone gives pleasure to the soul rather than the body; it therefore belongs to the realm of the neshamah, hinted in the pasuk "kol ha-neshamah tehallel" (let every neshamah praise).

כי הנשמה כ' בה ויפח באפיו נשמת חיים.

For of the neshamah it is written, "and He blew into his nostrils the breath of life" (Bereishis 2:7).

The neshamah was placed in man through the nostrils — "He blew into his nostrils" — so the nose and its sense of smell are the very gateway of the soul.

ואיתא בגמרא על פ' שפתותיו שושנים כל דיבור שיצא מפי הקב"ה נתמלא כל העולם בשמים.

And it is brought in the Gemara on the pasuk "his lips are roses" (Shir HaShirim 5:13): every utterance that came forth from the mouth of the Holy One, blessed be He, filled the entire world with fragrant spices.

The divine dibbur at Sinai literally perfumed the world; the holy speech of Hashem carries a spiritual fragrance that fills all of creation.

ומעין זה הנשמה יש בה מזה הריח.

And similar to this, the neshamah contains something of this fragrance.

A trace of that same holy fragrance of Hashem's speech is embedded within the neshamah of every Jew.

וע"ז חל הברכה.

And upon this the berachah rests.

Blessing settles specifically upon this fragrant inner point of the neshamah — which is why Yitzchak conferred the berachah by means of smell.

וכמו כן שבת יומא דנשמתין.

And likewise Shabbos is the "day of souls" (yoma d'nishmasin).

Shabbos is the day when the dimension of neshamah is revealed and dominant, the day of the soul.

והנשמה יתירה הבאה בשבת מג"ע ממנה בא הריח.

And the neshamah yeseirah (additional soul) that comes on Shabbos from Gan Eden — from it comes the fragrance.

On Shabbos a Jew receives an extra soul from Gan Eden, and this neshamah yeseirah brings with it that heavenly fragrance.

ולכן שורה בו ברכה ולכן מריחין בבשמים מוצ"ש לפי שנחסר זה הרית אחר השבת:

Therefore berachah rests upon it; and therefore we smell besamim (spices) at Motzaei Shabbos, because this fragrance is lacking after Shabbos.

Because blessing rests on the fragrant neshamah yeseirah, when Shabbos departs and that extra soul leaves, we smell besamim at Havdalah to console for the loss of its heavenly fragrance.

Summary: Smell is the sense of the neshamah, the one pleasure the soul enjoys rather than the body, rooted in the divine breath blown into man and in the fragrance that filled the world at Hashem's every utterance. Yitzchak — the root of yirah, like Mashiach who "smells and judges" — blessed by this inner fragrance; and the same explains the neshamah yeseirah of Shabbos and the besamim of Havdalah that compensate for its departure.