Milah opens the gates of revelation

במדרש ואחר עורי נקפו זאת כו'.

In the Midrash: "And after my skin has been struck off, this…" (Iyov 19:26).

The Midrash on this verse from Iyov serves as the Sefas Emes's springboard for discussing "skin" — a covering — both in the human body and in the spiritual realms.

כי הנה כמו שיש בגוף האדם עור ומכסה על הרמ"ח איברים כן הוא למעלה יש ג"כ מכסה כמ"ש במ"א דעוה"ז ועוה"ב הם מיני העלמות מצד עומק רום ועומק תחת.

For just as in the human body there is skin and a covering over the 248 limbs, so too Above there is likewise a covering, as is explained elsewhere, that This World and the World to Come are types of concealment, from the aspect of "the depth of height" and "the depth of below."

As the body's 248 limbs are wrapped in skin, the spiritual realms too have "coverings" that conceal the Divine light; This World and the Next World are each a kind of hiddenness, screening off the heights above and the depths below.

וכמו שהאדם זוכה להאיר אור נשמתו ולהעביר כסוי ערלת הגוף כן תוכל נשמתו להעלות למעלה לפתוח לה השערים הסגורים כנ"ל.

And just as a person merits to shine forth the light of his neshamah (soul) and to remove the covering of the body's "foreskin," so too his soul can ascend on high to open for itself the closed gates, as above.

When a person removes the "covering" that dims his soul — paralleling the milah that removes the foreskin — the light of his neshamah shines out, and that same soul can then rise upward and open the gates of heaven that were sealed before him.

וז"ש פתח האהל פתח טוב פתחת ע"י שעשה פתח בגופו בהסרת הערלה כן נפתח למעלה פתח האהל.

And this is the meaning of "the entrance of the tent" (Bereishis 18:1) — "a good entrance You have opened": because he made an "opening" in his body through the removal of the foreskin, so an opening of the tent was opened Above.

Avraham's bris milah created an "opening" in his body, and measure for measure this opened a corresponding "entrance" in the upper realms — the gates of revelation swung open because he had first opened himself through the mitzvah.

והוא יושב דמקודם לא הי' יכול לעמוד כדפרש"י בפסוק ויפול על פניו.

"And he was sitting" — for beforehand he had not been able to stand, as Rashi explains on the verse "and he fell on his face" (Bereishis 17:3).

Before the milah, when prophecy came to Avraham he was overwhelmed and fell on his face, unable to remain standing; the contrast highlights the change that the bris brought about in him.

ועתה שזכה להתגלות מכח מעשיו וז"ש וירא אליו כו' עי"ז נתישב הנבואה אצלו וז"ש במד' סימן לבניך כו'.

But now that he merited revelation by the power of his deeds — and this is "and Hashem appeared to him" (Bereishis 18:1) — through this the prophecy became settled within him; and this is what the Midrash says, "a sign for your children…"

Having earned revelation through the merit of the milah, Avraham could now receive prophecy in a settled, stable way rather than collapsing; the Midrash adds that this becomes a "sign" — an enduring gift — for his descendants.

פי' שזה שיושב היינו שא"צ להבטל מן המציאות כשבאה הנבואה אליו רק שמתישב ההארה בכל מעשיו:

The explanation: that he was "sitting" means that he no longer needed to be nullified out of existence when the prophecy came to him; rather, the illumination settled into all his deeds.

Avraham's "sitting" signifies that he no longer had to lose himself entirely (bittul) to receive Divine light; instead, the spiritual illumination could now rest and integrate within all his ordinary actions in this world.

Summary: Just as skin covers the body's limbs, "coverings" conceal the Divine light in the spiritual worlds. By performing the bris milah, Avraham removed the covering that dimmed his soul, and measure for measure an "entrance" was opened Above. Where before he had to collapse and be nullified to receive prophecy, now — "sitting" — the revelation could settle stably within him, allowing the holy illumination to rest within all his everyday deeds.