Avraham's hidden light reserved to bless the world

לך לך כו' ונברכו בך כו'.

"Go forth (lech lecha), etc., and through you shall be blessed, etc." (Bereishis 12:1-3).

The Sefas Emes opens with Hashem's command to Avraham to "go forth" and the promise that "through you all the families of the earth shall be blessed," which he will explain.

כי אאע"ה רצה לקרב כל הברואים אליו ית' אך הרשעים לא היו כדאי ליהנות מאורו כדכתיב וימנע מרשעים אורם ע"ש בזוה"ק.

For Avraham Avinu wished to draw all creatures near to Hashem; but the resha'im (wicked) were not worthy to derive benefit from his light, as it is written "and from the wicked their light is withheld" (Iyov 38:15); see there in the Zohar HaKadosh.

Avraham's whole desire was to bring all of mankind close to Hashem. But the wicked were unfit to benefit from his spiritual light, as the Zohar derives from the posuk that "from the wicked their light is withheld."

כמו דאיתא וירא אלקים האור כי טוב שהי' מאיר מסוף עולם וראה שאין כדאי לרשעים וגנזו כן הי' בחברהם אבינו ע"ה שהי' מוכן להאיר לעולם מראשו לסופו אך שלא הי' כדאי הרשעים וגנז הקב"ה אורו לבנ"י.

Just as it is stated, "and God saw the light, that it was good" (Bereishis 1:4) — that it shone from one end of the world (to the other), and He saw that it was not fitting for the wicked, and He hid it away — so it was with Avraham Avinu, who was ready to illuminate the world from its beginning to its end; but since the wicked were not worthy, the Holy One, blessed be He, hid away his light for Bnei Yisrael.

He draws a parallel to the Ohr HaGanuz, the primordial light: Hashem saw it would shine from end to end of the world, deemed it unfit for the wicked, and concealed it for the righteous. So too Avraham's light, capable of illuminating the whole world, was "hidden away" by Hashem and reserved for Bnei Yisrael.

ויבדל.

"And He separated (va-yavdel)."

Just as Hashem "separated" the primordial light from darkness, so a separation was made with Avraham — setting his light apart and reserved.

וא"ל לך לך כו' שיהי' מיוחד האור לו ולזרעו אחריו.

And He said to him, "Go forth, etc." — that the light should be reserved (meyuchad) for him and for his offspring after him.

The command "lech lecha" effected this very separation: by setting Avraham apart, his light became dedicated specifically to him and to his descendants, rather than dissipated upon the unworthy.

ובכח הבדל וגניזה זו ימשך אור מרחוק גם לכל העולם כמ"ש ונברכו בך כו'.

And by the power of this separation and concealment, light will be drawn from afar to the whole world as well, as it is written, "and through you shall be blessed, etc."

Paradoxically, it is precisely through concealing and reserving the light that it can ultimately reach the whole world — "from afar." By being guarded among Avraham's seed, the light is preserved so that in time "all the families of the earth shall be blessed through you."

ואברכה מברכיך פי' מו"ז ז"ל שעי"ז שייטב בעיני שאר אנשים דרכו של אברהם אע"ה יוכלו להיות בכלל הברכה ע"ש פ' וירא:

"And I will bless those who bless you" (Bereishis 12:3) — my grandfather, of blessed memory, explained that through this, when the way of Avraham Avinu finds favor in the eyes of other people, they can be included in the blessing; see there in Parashas Vayeira.

Citing his grandfather (the Chiddushei HaRim), the Sefas Emes explains "I will bless those who bless you": when others come to appreciate and find favor in Avraham's path, that very appreciation draws them into the orbit of the blessing — the means by which the reserved light eventually reaches the wider world.

Summary: Avraham yearned to draw all of creation close to Hashem, but the wicked were unworthy to benefit from his light. As with the primordial Ohr HaGanuz — which Hashem saw was unfit for the wicked and hid away for the righteous — Avraham's world-illuminating light was concealed and reserved, through "lech lecha," for him and his offspring. Yet it is precisely through this separation and concealment that the light is ultimately drawn "from afar" to bless the whole world: when others come to find favor in Avraham's path, they too are included in the blessing.