Oil Rising Through Avodah
ונתנך ה' כו' עליון במד' מה שמן צף למעלה כו'
"And Hashem will set you on high" (Devarim 28:1) — the Midrash explains this with the analogy of oil, which floats up above all other liquids.
The pasuk promises that one who listens to Hashem will be elevated, and the Midrash compares this to oil that always rises to the top above water.
כי זאת הברכה אשר אם נשמע בקול ה' ממילא ניתן האדם עליון על כל אף שהוא שפל עולה למעלה כמו השמן
For this is the blessing: that if we will but hearken to the voice of Hashem, then automatically a person is set on high above all, for even though he is lowly, he rises upward like the oil.
The blessing itself is conditional on hearkening to Hashem; once a person does so, he is automatically lifted above everything, just as oil rises despite being poured into a fuller liquid.
וביאור הדברים
And here is the explanation of the matter.
The Sfas Emes now introduces his explanation of how this elevation works.
כי אחז"ל הקב"ה למעלה ומשאו למטה היפוך ב"ו שמשאו על כתיפו
For Chazal taught that the Holy One, Blessed is He, is above while His burden is beneath Him — the opposite of flesh and blood, whose burden rests upon his shoulder.
Chazal teach that unlike a person who carries his load on top of himself, Hashem is above while what He sustains is held beneath Him.
ולכן בנ"י שהם קרובין למלך והם נושאין כל הנבראים לכן הם למעלה ג"כ מכולם דכ' תורה אור בר מצוה
Therefore Bnei Yisrael, who are close to the King and who bear up all created beings, are likewise above them all, as it is written, "For a mitzvah is a lamp and Torah is light" (Mishlei 6:23).
Since Bnei Yisrael are close to Hashem and carry the rest of creation through their avodah, they too stand above all, as the mitzvah is the lamp that holds the light of Torah.
ואור תורה היא חיות כל העולם ובנ"י ע"י המצות ועבודת הבורא עי"ז ממשיכין האור אחר הפתילה
And the light of Torah is the very life-force of the entire world, and Bnei Yisrael, through the mitzvos and the service of the Creator, thereby draw the light to follow after the wick.
The light of Torah gives life to the whole world, and through mitzvos and serving Hashem, Bnei Yisrael draw that light down to be absorbed by the wick.
וכמו שמן מעורב במים אשר הפתילה מוצאת מיד אף טפה קטנה של שמן ומעלת אותה מהמים
And just as with oil mixed into water, where the wick immediately finds even the tiniest drop of oil and raises it up out of the water,
He brings the image of a wick set in water with oil mixed in: the wick draws up even a minuscule drop of oil from amid the water.
כמו כן עולה כל עבודה קטנה שבלב איש ישראל עד למעלה והוא אורה לעולם כנ"ל:
so too does every small avodah within the heart of a Yid rise all the way upward, and it becomes a light to the world, as explained above.
In the same way, even the smallest act of avodah hidden in a Yid's heart is drawn all the way up and becomes a source of light for the world.
Summary: The Sfas Emes explains the pasuk "And Hashem will set you on high" through the Midrash's image of oil that floats above all other liquids. He builds on Chazal's teaching that, unlike flesh and blood who carries his burden upon himself, Hashem is above while all of creation is sustained beneath Him. Because Bnei Yisrael are close to the King and bear up all created beings through Torah and mitzvos, they too are elevated above everything, for the mitzvah is the lamp that holds the light of Torah which gives life to the world. Just as a wick draws even the tiniest drop of oil up out of the water in which it is mixed, so too every small avodah within the heart of a Yid is drawn all the way upward and becomes a light to the world.