Blessing as reconnection to the root

בפרשת נשיאות כפים איתא במד' שהבטיח הקב"ה לאברהם אבינו והי' ברכה שנמסרו הברכות בידו.

Regarding the parsha of nesias kapayim (the priestly blessing), the Midrash says that the Holy One promised Avraham Avinu, "and you shall be a blessing" (Bereishis 12:2) - that the blessings were handed over into his hand.

The power to bless was entrusted to Avraham, as Hashem told him "you shall be a blessing," meaning that the keys of blessing were placed in his control.

ונשאר זה אצל הכהנים.

And this remained with the kohanim.

That bestowed power of blessing carried down through Avraham's descendants and remained specifically with the kohanim, who descend from him.

כי עיקר הברכה הוא בהתעלות הדברים אל השורש.

For the essence of blessing is the elevation of things back to their root.

True blessing is not merely added good but the raising of every thing back up to its source in Hashem, where all abundance flows from.

וזה הי' מדת אאע"ה כמ"ש אחות לנו שאיחה כל העולם להקב"ה.

And this was the trait of Avraham Avinu, as it is said, "we have a sister" - that he "stitched" the whole world together to the Holy One.

The word "achos" (sister) is read like "ichah" (he joined/mended): Avraham's avodah was to bind and reconnect the entire world back to Hashem, which is the very work of elevating things to their root.

וזה ברכה בריכה כמ"ש במד'.

And this is "berachah" (blessing) in the sense of "bereichah" (a pool/spring), as the Midrash says.

Blessing is likened to a spring or reservoir: it is the channel through which everything is connected to and drawn from its flowing source.

וכן מדת הכהן דכתי' ממנו יתד זה כ"ג ותקעתיו יתד.

And so too is the trait of the kohen, as it is written, "from him comes the peg" - this refers to the Kohen Gadol - and "I will fix him as a peg" (Yeshayah 22:23).

The kohen is compared to a tent-peg driven firmly into place: he is the anchor that fastens the people to their root above.

פי' כח התחברות אל השורש וממילא חל הברכה.

Meaning: the power of connection to the root, and as a result the blessing automatically takes hold.

The "peg" represents the power to connect to the source; once that connection is made, blessing flows of its own accord.

ז"ש אמור להם כמ"ש האמרת עשית חטיבה אחת שמתחברין נפשות בני ישראל אל השורש.

This is the meaning of "say to them" (Bamidbar 6:23), as in "you have distinguished" (he'emarta) - you have made one unified entity - that the souls of Bnei Yisrael become bound to the root.

The Torah's word "amor" (say) is linked to "he'emarta" (you have set apart/declared as one): the kohen's blessing fuses the souls of Bnei Yisrael into a single unified bond with their root in Hashem.

ויש בברכת כהנים ו' ברכות יברכך ישמרך יאר ויחונך ישא שלום.

And there are six blessings in Birkas Kohanim: "may He bless you," "and guard you," "may He shine," "and be gracious to you," "may He lift," "[and grant] peace."

The priestly blessing contains six distinct expressions of blessing, corresponding to the six.

אח"כ כתיב סתם ואני אברכם.

Afterward it is written, without specification, "and I will bless them" (Bamidbar 6:27).

After the six detailed blessings comes one final, unspecified blessing straight from Hashem Himself: "and I will bless them."

והוא רמז לבחי' ששת ימי המעשה שמתחברין בשבת.

And this hints at the aspect of the six days of work, which become joined together in Shabbos.

The six blessings correspond to the six weekdays, and Hashem's seventh, all-encompassing blessing corresponds to Shabbos, which gathers and unites all six.

ואז חל עיקר הברכה כמ"ש בזוה"ק דכל ברכאין בי' תליין ולכן לא אשתכח בי' מנא.

And then the essence of the blessing takes hold, as the Zohar says that all blessings depend on it (Shabbos), and therefore the manna was not found on it.

The Zohar teaches that all blessing flows from Shabbos as its source. Precisely because it is the wellspring of all blessing, the manna did not fall on Shabbos - its abundance was already drawn down from that day into the rest of the week.

וזה ואני אברכם שורש הברכות כולן:

And this is "and I will bless them" - the root of all the blessings.

Hashem's own concluding blessing is the source-blessing of Shabbos, the root from which all the individual blessings of the week derive.

Summary: The essence of blessing is reconnecting everything to its root in Hashem - the trait of Avraham, who "stitched" the world back to its Source, and of the kohen, the firm "peg" who binds Bnei Yisrael's souls to that root. The six expressions of Birkas Kohanim parallel the six weekdays, while Hashem's own final "and I will bless them" is the all-encompassing blessing of Shabbos, the wellspring from which every other blessing flows.