Inner Torah Rectifies Worlds
לא נפלאת הוא ממך כו' במד' דכ' נעלמה מעיני כל חי מלאכים חיות הקודש כו' וממך לא נפלאת
"It is not too wondrous for you" (Devarim 30:11) — the Midrash expounds on the verse "It is hidden from the eyes of all living" (Iyov 28:21), that the inner depths of the Torah are concealed even from the angels and the holy Chayos, and yet "from you it is not hidden."
The Sfas Emes opens with the verse that the Torah is not beyond reach for Bnei Yisrael, and cites the Midrash that the Torah's inner depths are hidden even from the angels — yet not from a Jew.
ביאור הענין ע"פ מ"ש האר"י ז"ל כי המלאכים הם מבחי' חיצוניות העולמות ונשמות בנ"י מפנימיות כו'
The explanation of this matter is according to what the Arizal wrote, that the angels are from the aspect of the externality of the worlds, whereas the neshamos of Bnei Yisrael are from the innermost dimension.
He brings the Arizal's teaching that angels belong to the outer surface of creation, while Jewish neshamos are rooted in its innermost core.
לכן עבודת האדם רק בחיצוניות לתקן זאת
Therefore, the avodah of a person is needed only in the external realm, in order to set that domain right.
Since a person stands rooted in the inner dimension, his task in this world is specifically to fix and elevate the external realm.
וכן המלאכים להם קשה לתקן הפנימיות כי זה לעומת זה עשה הקב"ה בעבור כי לנו הפנימיות צריכין לתקן החיצוניות
And likewise the angels — for them it is difficult to rectify the inner dimension, for "the Holy One, Blessed is He, made one corresponding to the other" (Koheles 7:14): because the inner dimension is ours, we are the ones who need to rectify the externality.
Conversely, the angels cannot reach the inner dimension; Hashem arranged the worlds as a mirror-image so that each rectifies what the other cannot, and the inner work belongs to Bnei Yisrael.
וז"ש קרוב אליך כו' בפיך ובלבבך הוצא דבר מתוך פיך פי' כי בפנימיות אין חוסר לנו
This is the meaning of "it is very close to you, in your mouth and in your heart" (Devarim 30:14) — "bring forth a word from your mouth" — meaning that as far as the inner dimension is concerned, we lack nothing.
The verse "in your mouth and in your heart" teaches that in the inner realm — heart and speech — Bnei Yisrael are fully equipped and lack nothing.
ומעיני כל חי הוא הסתכלות החיצוניות והוא מלאכים וחיה"ק
And "the eyes of all living" refers to gazing upon the externality, and this is the realm of the angels and the holy Chayos.
The phrase "the eyes of all living" denotes the perspective of the external worlds, which is the domain of the angels and the holy Chayos.
והם תלוין בעבודת האדם כפי מה שמקבלין התורה והמצות מאיר להם פנימיות התורה ג"כ והם מצפין למעש"ט של ישראל כמ"ש בזוה"ק בכמה דוכתי:
And they are dependent upon the avodah of a person: according to the measure in which Bnei Yisrael receive the Torah and the mitzvos, the inner light of the Torah shines for the angels as well, and they look longingly toward the good deeds of Bnei Yisrael, as is stated in the holy Zohar in several places.
The angels themselves depend on the avodah of Bnei Yisrael: when a Jew receives Torah and mitzvos, the Torah's inner light radiates to them too, so they yearn for the good deeds of Bnei Yisrael, as the Zohar repeatedly says.
Summary: The Sfas Emes explains why the Torah, though hidden even from the angels and the holy Chayos, is "not too wondrous" for Bnei Yisrael. Drawing on the Arizal, he teaches that the angels are rooted in the externality of the worlds while the neshamos of Bnei Yisrael are drawn from their innermost dimension. Because each was made as a counterpart to the other, the angels cannot rectify the inner realm and must labor in the external, while Bnei Yisrael, who possess the inner dimension, are tasked with rectifying the external world. Thus the verse "in your mouth and in your heart" assures us that in the inner realm we lack nothing. Ultimately the angels themselves depend on the avodah of Bnei Yisrael, for when a Jew receives Torah and mitzvos the inner light of the Torah shines upon them too, and they look longingly toward the good deeds of Bnei Yisrael.