Daily Renewal Through Tefillah
א"נ היום כו' פי' בכל יום כמ"ש יהי' בעיניך כחדשים כמ"ש היום אם בקולו תשמעון
It says, "This day [you stand before Hashem your God]" (Devarim 29:9) — meaning on every single day, as it is taught, "They should be in your eyes like new" (Rashi on Devarim 26:16), and as the pasuk says, "Today, if you would but hearken to His voice" (Tehillim 95:7).
The pasuk's word "this day" teaches that standing before Hashem is not a one-time event but a daily reality — each day the Torah and avodah must feel fresh and new.
וע"י ההתחדשות יכול כל איש ישראל ליישר עצמו להיות עומד לפני הש"י
And it is through this constant renewal that every Jew is able to set himself straight, to stand before Hashem Yisborach.
This daily sense of renewal is precisely what empowers a Jew to straighten himself out and stand in Hashem's presence.
וחז"ל פי' עמידה זו תפלה שהיא נגד ח"י חוליות שיוכל האדם להעמיד עצמו לפניו ית'
And Chazal explained that this "standing" refers to tefillah, which corresponds to the eighteen vertebrae [of the spine, paralleling the eighteen berachos of Shemoneh Esrei], through which a person is able to establish himself standing before Him Yisborach.
Chazal identify this "standing" as tefillah, which mirrors the eighteen vertebrae of the spine and the eighteen berachos of Shemoneh Esrei — the means by which a person plants himself upright before Hashem.
ולכן מקדימין ק"ש קודם התפלה שהוא הקבלה מצוך היום כו' להיות מקבל האדם עליו מ"ש ומצותיו כאלו עימד על הר סיני
And therefore we recite Kerias Shema before the tefillah, for that is the acceptance [of the yoke of Heaven] — "[that] He commands you this day" (Devarim 27:10) — that a person should take upon himself the yoke of Heaven and His mitzvos as though he were standing at Har Sinai.
We say Kerias Shema before Shemoneh Esrei because Shema is the act of accepting the yoke of Heaven and the mitzvos anew, as if one were receiving them at Har Sinai that very day.
וע"י ההתחדשות בק"ש יכול להיות עומד אח"כ בתפלה
And through the renewal that comes by way of Kerias Shema, a person is then able to stand afterward in tefillah.
Once a person has renewed his acceptance of the yoke of Heaven through Shema, he is then prepared to truly stand in tefillah.
ועיקר העצה לזה הוא בחי' כולכם שהוא כלל הצריך לפרט
And the essential counsel for this is the aspect of "all of you" (Devarim 29:9) — which is the general whole that requires the particular detail.
The key to achieving this renewal is the dimension of "all of you" — the collective klal, which gives life and meaning to each individual detail.
ומ"מ הפרט צריך לכלל וכשמכניס עצמו בכלל ישראל נאמר א"נ כולכם כו':
And nonetheless the particular individual requires the general whole, and when a person brings himself into the klal of Bnei Yisrael, it is said of him, "This day all of you [stand before Hashem]" (Devarim 29:9).
Yet the individual also needs the klal, and only when a person joins himself to Klal Yisrael does the pasuk's promise of "this day all of you stand" apply to him.
Summary: The Sfas Emes explains that the words "this day you stand before Hashem" point to a daily, ever-renewing avodah, for the Torah must always feel new in our eyes. This renewal is what enables every Jew to straighten himself and stand before Hashem, and Chazal identify this "standing" with tefillah, which parallels the eighteen vertebrae of the spine and the eighteen berachos of Shemoneh Esrei. We precede tefillah with Kerias Shema because Shema is the renewed acceptance of the yoke of Heaven and the mitzvos, as though one stood at Har Sinai that very day, and only after this renewal can a person genuinely stand in tefillah. The Sfas Emes concludes that the essential counsel for attaining this renewal is the aspect of "all of you" — the klal — for the individual draws his life and standing before Hashem only by binding himself to Klal Yisrael.