Listening Elevates The Mind
במדרש אשרי שומע לי לשקוד ע"ד דלת לפנים מדלת כו' ובמד' תנחומא שמוע בעוה"ז תשמע בעוה"ב כי הגוף מלבוש הנשמה וצריך מקודם פתיחת הלב הגשמיי ואח"כ צריך לפתיחות שורש נשמתו וזהו בא ממילא
The Midrash expounds the verse "Praiseworthy is the one who listens to Me, to be diligent at My doors day by day" (Mishlei 8:34) as referring to door within door; and the Midrash Tanchuma teaches that "if you will surely listen" means that one who listens in this world will merit to listen in Olam Haba, for the body is the garment of the neshamah, so that first there must be an opening of the physical heart, and afterward there must be an opening of the very root of one's neshamah, and this latter opening comes of itself.
Listening in this world earns the ability to truly listen in Olam Haba. Since the body clothes the neshamah, a person first opens his physical heart through his own effort, and then the deeper opening of his soul's root follows automatically.
וכפי עבודת האדם בימי המעשה נפתח לו בש"ק מעין עוה"ב לכן שמוע תשמעו בקולי ר"ת שבת
And according to a person's avodah during the weekdays, on the holy Shabbos there is opened up for him a foretaste of Olam Haba; therefore the words "if you will surely listen to My voice" (shamoa tishme'u) have as their initial letters the word Shabbos.
A person's weekday avodah determines how much of a taste of Olam Haba opens to him on Shabbos. The Sfas Emes notes that the initial letters of "shamoa tishme'u b'koli" spell Shabbos.
גם פי' תשמע לאחרים ע"ש במד' דאיתא מקודם יקבל עליו עול מלכות ש' ואח"כ עול מצות
There is also another interpretation, that "you will cause others to listen," based on what the Midrash states, that first a person accepts upon himself the yoke of the Kingship of Heaven and afterward the yoke of the mitzvos.
A second reading of "you will cause others to listen" is anchored in the Midrash's order: first accept the yoke of Hashem's Kingship, then the yoke of mitzvos.
כי באמת התפשטות השכל וההשגה תוך המעשים זה בחי' עול מצות ומקודם פ' שמע היא הבנה והשגת הדעת כמ"ש דע כו' אלקי אביך
For in truth the spreading of the intellect and comprehension into one's deeds is the aspect of the yoke of mitzvos, and beforehand the parshah of Shema is understanding and the grasp of the mind, as it is written, "Know the God of your father and serve Him" (Divrei HaYamim I 28:9).
Drawing one's intellect into actual deeds is the yoke of mitzvos. The Shema itself comes first as pure understanding and grasp of the mind, as the verse couples knowing Hashem with serving Him.
אח"כ שמע תשמעו היא להשמיע בפה להכניס דברים אלו לאיברי הגוף הוא באמת ע"י כח הפה שבנ"י כחן בפה
Afterward, "you will surely listen" (shamoa tishme'u) means to make these matters heard with the mouth, to bring them into the limbs of the body, and this is truly accomplished through the power of the mouth, for the strength of Bnei Yisrael lies in their mouth.
"Shamoa tishme'u" then means voicing these truths aloud so they enter the body's limbs. This works specifically through the power of speech, since the strength of Bnei Yisrael is in their mouth.
וזה בחי' ועבדהו במצות כמ"ש לעבדה ולשמרה בעשה ול"ת כו' וכפי התפשטות הדעת במעשים כמו כן מתרבה הדעת
And this is the aspect of "and serve Him" through the mitzvos, as it is written, "to work it and to guard it" (Bereishis 2:15) — corresponding to the positive and negative commandments — and according to the spreading of the mind into one's deeds, so too the mind itself is increased.
This voiced service is "and serve Him" through the mitzvos, paralleling "to work it and to guard it" as the positive and negative commandments. The more the mind spreads into action, the more the mind itself grows.
וז"ש במד' ע"י שעונין אמן בעוה"ז זוכה לענות אמן בעוה"ב
And this is what the Midrash means, that through answering Amen in this world one merits to answer Amen in Olam Haba.
The Midrash's teaching that answering Amen here earns answering Amen in Olam Haba reflects this same growth of the mind.
ופרשנו כבר
And we have already explained this elsewhere.
The Sfas Emes notes that he has already treated this idea in another place.
ותוכן הדברים כמו שהי' המצוה שהלוים יאמרו וכל העם יענו אמן
The content of the matter is just as it was with the mitzvah that the Leviim would proclaim and all the people would answer Amen.
The essence corresponds to the mitzvah at Har Gerizim and Har Eival, where the Leviim called out and the entire people answered Amen.
היינו שאף פשוטי ב"א שא"י להבחין שזה ברכה וזה קללה אעפ"כ ע"י ענית אמן שמבקשין להימשך אחר אנשי אמת יש להם תיקון, וכמו כן באדם עצמו ע"י התמשכות כלי המעשה אחר הדעת שבו ועונה אמן בע"כ
That is to say, that even simple people who are unable to discern that this is a blessing and that is a curse, nevertheless, through their answering Amen — by which they seek to be drawn after the people of truth — they have a tikkun; and likewise within a person himself, through the drawing of the instruments of action after the mind within him, he answers Amen even against his will.
Even simple people who cannot distinguish blessing from curse gain a tikkun by answering Amen, attaching themselves to the people of truth. So too within a person, his limbs of action are drawn after his mind and answer Amen even against their will.
והשי"ת משלם לו ג"כ שהשכל והדעת מתעלה ג"כ אף למקום שלמעלה מהשגתו כמו שהמשיך המעשה להיבטל להדעת ובמ"א הארכנו בפי' ב' עולמות אלו:
And Hashem Yisbarach in turn rewards him, for the intellect and the mind are also elevated, even to a place that is above its own comprehension, just as the deed was drawn to be nullified to the mind; and elsewhere we have expounded at length the explanation of these two worlds.
Hashem rewards this by elevating the mind itself to a place beyond its own grasp, just as the deeds were nullified to the mind. The Sfas Emes notes he has elaborated elsewhere on these two worlds.
Summary: The Sfas Emes explains that listening in this world earns one the ability to listen in Olam Haba, because the body is the garment of the neshamah: a person must first open his physical heart through weekday avodah, and then the opening of his soul's root follows on its own, with Shabbos granting a foretaste of Olam Haba. He maps the progression of "shamoa tishme'u" onto two stages of avodah — first the Shema as pure understanding and grasp of the mind, and then voicing these truths aloud so they penetrate the limbs of the body, drawing on the unique power of speech given to Bnei Yisrael. As the intellect spreads into one's deeds, the mind itself is increased, which is the meaning of the Midrash that answering Amen in this world merits answering Amen in Olam Haba. Just as simple people gained a tikkun at Har Gerizim and Har Eival by answering Amen and attaching themselves to the people of truth, so too within a person his instruments of action are nullified to his mind and answer Amen even against their will. In reward, Hashem Yisbarach elevates that person's mind to a place above its own comprehension, mirroring how his deeds submitted themselves to his mind.