Speech as Soul's Lifeforce
בפסוק מוצא שפתיך תשמור אחז"ל מ"ש מ"ע תשמור מל"ת
On the pasuk "That which goes forth from your lips you shall keep" (Devarim 23:24), Chazal expounded that the phrase "that which goes forth" hints to a positive mitzvah, and "you shall keep" hints to a negative mitzvah.
The Sfas Emes opens with the Chazal that the verse about keeping the words of one's lips alludes to both a positive command and a negative command embedded in the act of speech.
הרמז כי כל תרי"ג מצות תלוין בזה כי עיקר חיות הנשמה בפה כמ"ש ויפח באפיו כו' לנפש חי' רוח ממללא
The deeper hint here is that all six hundred and thirteen mitzvos depend upon this, for the essence of the neshamah's life-force resides in the mouth, as it is written, "And He breathed into his nostrils a living soul" (Bereishis 2:7) — which Targum renders as a speaking spirit.
He explains that speech is the root of all mitzvos because the neshamah's vitality flows through the mouth, as the Torah describes man being given a soul that is, in Targum's words, a speaking spirit.
וע"י המצות נפתח חיות הנשמה וע"ז כ' אשר יעשה כו' האדם וחי בהם שנעשה נפש חי'
It is through the mitzvos that the life-force of the neshamah is opened, and concerning this it is written, "which a man shall do and live by them" (Vayikra 18:5), meaning that he becomes a living soul.
Performing mitzvos unlocks and channels the neshamah's life-force, which is why the Torah says a person 'lives' through the mitzvos — he becomes a truly living soul.
ומ"ע לפתוח הפה
The positive mitzvah is to open the mouth.
The positive aspect of speech is the obligation to open one's mouth and use it for holiness.
ומל"ת לשמור שלא יתפשט כח הנשמה לסט"א ח"ו וזה עיקר כח איש ישראל כמ"ש ואשים דברי בפיך וזה ניתן לבנ"י במתן תורה
And the negative mitzvah is to guard oneself, that the power of the neshamah not spread over to the Sitra Achra, chas v'shalom; and this is the essential strength of a Yid, as it is written, "And I have placed My words in your mouth" (Yeshayahu 51:16), and this was given to Bnei Yisrael at Matan Torah.
The negative aspect is to guard that the neshamah's power is not drawn toward the forces of impurity; the strength of a Yid lies in Hashem placing His words in his mouth, a gift granted at Matan Torah.
ז"ש כאשר נדרת לה"א כמ"ש אשר דיבר ה' נעשה שקיבלו בנ"י על עצמן לברר הנהגת הש"י בעולם דבר ה' היא הנהגה שלו והיא נגנז בתורה בעשרה מאמרות ועשרת הדיברות
This is the meaning of "as you have vowed to Hashem your God," like the words "that which Hashem has spoken we shall do," for Bnei Yisrael took upon themselves to clarify and reveal Hashem's governance in the world — for the word of Hashem is His mode of conducting the world, and it lies concealed within the Torah, in the Ten Utterances of Creation and the Ten Dibros.
The vow 'as you have vowed to Hashem' reflects the commitment of Bnei Yisrael to reveal Hashem's hidden governance in the world, a governance concealed within the Torah in the Ten Utterances and the Ten Dibros.
נדבה אשר דברת יתכן לרמוז על הקדמת נעשה לנשמע שהיא נדבה ברצון טוב ביותר למעלה מן הטבע
The phrase "a free-will offering, that which you have spoken" (Devarim 23:24) may be understood as a hint to the precedence of na'aseh before nishma, which is a free-will offering given with the very finest goodwill, above and beyond the natural order.
The 'free-will offering that you have spoken' hints to the precedence of na'aseh over nishma, a wholehearted gift offered above nature.
[ויובן שפיר לפמ"ש בענין הקדמת נעשה לנשמע]:
[And this will be well understood according to what we have explained regarding the precedence of na'aseh before nishma.]
He closes by noting this fits beautifully with his earlier teaching on why Bnei Yisrael placed na'aseh before nishma.
Summary: The Sfas Emes teaches that the mitzvah to keep the words of one's lips encompasses both a positive and a negative command, and that speech itself is the root of all six hundred and thirteen mitzvos, since the neshamah's vitality is centered in the mouth — man being a 'speaking spirit.' Through performing mitzvos the life-force of the neshamah is opened, so that a person truly becomes a living soul; the positive command is to open the mouth in holiness, while the negative command is to guard that this power not be drawn toward the Sitra Achra. This power of speech is the unique strength of a Yid, given at Matan Torah when Hashem placed His words in our mouths, empowering Bnei Yisrael to reveal Hashem's concealed governance of the world hidden within the Torah in the Ten Utterances and the Ten Dibros. The 'free-will offering you have spoken' hints to the precedence of na'aseh before nishma — a wholehearted gift offered above the natural order.