Guarding speech expands the inner will

ובמד' תנחומא לעשות רצונך כו' חפצתי ותורתך בתוך מעי.

And in the Midrash Tanchuma: "To do Your will, I desired, and Your Torah is within my innards" (Tehillim 40:9).

The Sefas Emes builds on the pasuk that the ratzon (will) to do Hashem's will, and His Torah, are planted deep within a person.

בכל דבר נתן השי"ת מצוה ע"ש שיש בכל איש ישראל רצון אמת להשי"ת כמ"ש ז"ל לעולם יראה אדם כאלו קדוש שרוי בתוך מעיו.

In everything Hashem placed a mitzvah — because in every Yid there is a true ratzon (will) toward Hashem, as Chazal said: "A person should always regard himself as though a holy one dwells within his innards."

Every mitzvah corresponds to an inner true will toward Hashem that resides in each Yid; one must view oneself as housing something holy within.

אך הצרה בצדה הרצונות אחרים שנמצאים באדם מכח היצה"ר והם גורמים שלא יוכל רצון אמת להתרחב בלב כראוי.

But the trouble is alongside it: the other desires found in a person from the power of the yetzer hara, which prevent the true will from expanding in the heart as it should.

Foreign desires driven by the yetzer hara crowd the heart and block the true inner will from spreading and filling it.

וז"ש שומר פיו ולשונו שומר מצרות נפשו.

And this is the meaning of "One who guards his mouth and his tongue guards his nefesh (soul) from troubles."

The pasuk (Mishlei 21:23) is read with "nafsho" understood as one's will — guarding speech guards the will.

נפש הוא הרצון כמ"ש יש את נפשכם וע"ז נאמר אל תשקצו את נפשותיכם כי אם הרצון אינו משוקץ ממילא מתרחב רצון אמת שבלב איש ישראל להשי"ת.

"Nefesh" means the will, as it says "if it is your nefesh (will)" (Bereishis 23:8); and concerning this it is said, "Do not make your souls detestable" — for if the will is not made detestable, then automatically the true will in the heart of a Yid toward Hashem expands.

Connecting the parsha's warning (Vayikra 11:43) about not defiling one's nefesh through forbidden creatures: keep the will untainted, and the true will toward Hashem naturally grows.

וז"ש בשרצים (אנכי ה' אלקיך המעלך) [*אני ה' המעלה אתכם] מארץ מצרים כי השי"ת הוציא את בנ"י ממיצר ולכן אם כך הוא ישמור עצמו מלשקץ הרצון.

And this is why regarding the creeping creatures it says, "I am Hashem who brings you up from the land of Mitzrayim" — for Hashem took Bnei Yisrael out from the narrow straits (meitzar); therefore, if so, one should guard himself from defiling the will.

The Torah attaches the Exodus to the laws of forbidden creatures: just as Hashem freed Bnei Yisrael from the "narrow place" of Mitzrayim, so should a person free his will from constriction by not defiling it.

ממילא יוכל להתרחב ולהמשיך כל הגוף להבורא ית'.

Then automatically it can expand and draw the entire body toward the Creator, may He be blessed.

An untainted will broadens and pulls even the physical body along after Hashem.

וז"ש אנכי המעלך מארץ מצרים הרחב פיך הוא באמת שמירת פה ולשון שעי"ז השמירה יוכל להתרחב כמ"ש ואמלאהו.

And this is the meaning of "I am the One who brings you up from the land of Mitzrayim, open wide your mouth" (Tehillim 81:11) — this is truly the guarding of mouth and tongue, for through that guarding one is able to expand, as it says, "and I will fill it."

"Open wide your mouth and I will fill it" is fulfilled precisely through guarding the mouth: restraint from evil speech is what allows the inner will to widen and be filled by Hashem.

איברא גם זה אמת שאם אדם מתדבק היטב במצוה וממשיך כל נפשו ורצונו להשי"ת עי"ז לא יבוא ג"כ לידי רצון אחר וז"ש התרפית ביום צרה צר כחכה מכלל שאם הי' מתחזק בטוב כראוי לא הי' לו מצר ע"י יום צרה כלל כנ"ל:

Indeed, this too is true: if a person cleaves well to the mitzvah and draws all his nefesh and will toward Hashem, through this he will also not come to any foreign desire. And this is the meaning of "If you showed yourself slack in the day of distress, your strength is narrow" (Mishlei 24:10) — implying that had he strengthened himself in the good as he should, he would have had no constriction from the "day of distress" at all, as above.

The flip side: cleaving fully to mitzvos channels the whole will to Hashem and crowds out foreign desires. The pasuk hints that "slackness" alone causes the narrowness; proper strength in good would leave no room for distress to constrict a person.

Summary: Every Yid carries a true inner will toward Hashem, but foreign desires from the yetzer hara constrict the heart and block it. Guarding the mouth and tongue — keeping the will undefiled — is the avodah that frees this will from its "Mitzrayim," letting it expand and draw the whole body after the Creator. "Open wide your mouth and I will fill it": restraint of speech opens the way for Hashem to fill the heart.