Bittul to Hashem as the source of all blessing

במדרש כה תברכו וכו' ואעשך לגוי גדול והי' ברכה כו' ע"ש.

In the Midrash on "Thus shall you bless" (Bamidbar 6:23), etc.: "And I will make you into a great nation… and you shall be a blessing" (Bereishis 12:2), etc. - see there.

The Midrash links the priestly blessing ("thus shall you bless") to Hashem's promise to Avraham that he himself would become a blessing.

הענין הוא שהקב"ה וב"ש אמר לאברהם אע"ה לך לך מארצך כו'.

The matter is that the Holy One said to Avraham Avinu, "Go for yourself, from your land…" (Bereishis 12:1), etc.

Hashem commanded Avraham to leave behind his land, birthplace, and father's house - a call to separate from his natural surroundings.

וביטל כל הטבע ופירש עצמו מכולם ועי"ז עצמו נעשה הוא הברכה ונמשך קיום העולם על ידו להודיע כי קיום כל הטבע ע"י הביטול אליו ית'.

And he nullified all of nature and separated himself from everyone; and through this very act he became "the blessing," and the existence of the world was drawn through him - to make known that the sustaining of all of nature is through bittul (self-nullification) to Hashem.

By nullifying nature and detaching himself from his surroundings to cleave to Hashem, Avraham himself became the source of blessing through which the world endures - teaching that the whole natural order is sustained precisely by such bittul to Hashem.

וכמו כן נתקיים בבנ"י בכלל שהם הנפרשין מאנשי הטבע ובפרט במדבר שנמשכו אחריו ית' למקום מדבר שממה ולכן נמסר הברכה בידיהם.

And likewise it was fulfilled in Bnei Yisrael as a whole, who are the ones separated from the people of nature - and in particular in the wilderness, when they followed after Hashem to a place of desolate desert; therefore the blessing was entrusted into their hands.

Bnei Yisrael continue Avraham's path: they stand apart from "the people of nature," most strikingly when they followed Hashem into the barren midbar. Because of that bittul, the power of blessing was placed in their hands.

ובפרט הכהנים שאין להם חלק בארץ והיו מופרשים רק לעבודת המקדש והיו הם המברכים לכל.

And in particular the Kohanim, who have no portion in the land and were set apart only for the avodah of the Mikdash - they were the ones who blessed everyone.

The Kohanim embody this separation most fully: owning no land and devoted entirely to the service of the Bais Hamikdash, they became the conduits of blessing for all of Bnei Yisrael.

ומה"ט נסמכה פרשה זו לפרשת נזיר לומר שע"י הנזירה והפרישה מן הטבע שורה הברכה בהטבע וביטולו של דבר זה קיומו.

And for this reason this passage (the priestly blessing) is placed next to the passage of the nazir, to teach that through nezirus and separation from nature, blessing rests upon nature - and the nullification of a thing is its very existence.

The Torah juxtaposes the nazir with the priestly blessing to teach the same principle: it is by abstaining and separating from the natural that one draws blessing down into nature. The "nullification" of a thing - rising above it for Hashem's sake - is paradoxically what gives it lasting existence.

ומה"ט בש"ק יורד ברכה על כל ימי המעשה ע"י שיש בו ביטול הטבע וכל מעשה גשמיי לכן היא מקור הברכה.

And for this reason, on Shabbos Kodesh blessing descends upon all the days of labor - because it contains the nullification of nature and of all physical activity; therefore it is the source of blessing.

Shabbos too embodies bittul of nature, for on it we cease all melachah and physical creating; that very cessation is why Shabbos becomes the wellspring of blessing for the entire week.

והג' סעודות בש"ק הם מעין הג' ברכות שבברכת כהנים.

And the three meals (seudos) of Shabbos Kodesh are a reflection of the three blessings in the priestly blessing (Birkas Kohanim).

The three Shabbos meals mirror the threefold structure of the priestly blessing, each drawing down a measure of that same blessing rooted in bittul.

וזה ג"כ הרמז בפסוק ואיש את קדשיו לו יהיו ודו"ק:

And this too is the hint in the pasuk, "and each man's holy things shall be his" (Bamidbar 5:10) - examine it carefully.

The Sefas Emes suggests that this pasuk also alludes to the principle that what a person sanctifies and sets apart for Hashem - his "holy things" of bittul - is precisely what truly becomes his own and endures.

Summary: When Avraham nullified nature and separated himself from his surroundings to cleave to Hashem, he himself became "the blessing" through which the world endures - teaching that all of nature is sustained by bittul to Hashem. Bnei Yisrael inherit this path as those set apart from "the people of nature," especially in following Hashem into the wilderness, and above all the Kohanim, who own no land and serve only in the Mikdash, becoming the bearers of blessing. The juxtaposition of the nazir, the cessation of Shabbos, and the three Shabbos meals all reflect the same truth: the nullification of a thing for Hashem's sake is the secret of its lasting existence and the source of blessing.