Revealing The Neshamah Through Battle

בפסוק כ"ת מחנה כו' ה"א מתהלך בקרב מחנך

Regarding the verse, "When the camp goes out... for Hashem your God walks in the midst of your camp" (Devarim 23:15).

The Sfas Emes opens with the verse describing Bnei Yisrael going out to war, where the Torah promises that Hashem Himself accompanies them within their camp.

כשאדם מכין עצמו למלחמות מצוה מסייע לו כח הנשמה דאיתא לעולם יראה אדם עצמו כאלו קדוש שרוי בתוך מעיו

When a person prepares himself for the battles of a mitzvah, the power of his neshamah comes to his aid, as the Gemara teaches: a person should always view himself as though a holy being dwells within his innards.

When a Jew girds himself for the struggles demanded by a mitzvah, his neshamah empowers him, since the Gemara says one must always regard himself as housing something holy within.

ונקודה הקדושה טמונה בו וע"י המלחמה מתגלה ומתפשט כח הנשמה בכל האברים

The holy point lies concealed within him, and through the battle the power of the neshamah is revealed and spreads forth into all the limbs.

Hidden inside every person is a sacred point, and the very act of waging the battle draws out the strength of the neshamah so that it permeates the entire body.

וכמו שזוכין בשבת לבחי' נשמה יתירה ע"י המנוחה כמו כן בימי המעשה ע"י המלחמה לשם שמים:

And just as on Shabbos one merits the level of the neshamah yeseirah (the additional soul) by means of menuchah (rest), so too during the weekdays one merits this through doing battle for the sake of Heaven.

The avodah of the weekday battle parallels Shabbos: on Shabbos the extra soul is attained through rest, while on weekdays it is attained through fighting purely for the sake of Heaven.

Summary: The Sfas Emes builds on the verse that Hashem walks within the camp of Bnei Yisrael when they go out to war. He explains that whenever a person mobilizes himself for the battles entailed by a mitzvah, the strength of his neshamah rises up to assist him, in keeping with the Gemara's teaching that one should always see himself as though a holy being dwells within him. This concealed holy point is precisely what gets revealed through the struggle, spreading the power of the neshamah throughout all the limbs. The Sfas Emes draws a parallel to Shabbos: just as the neshamah yeseirah is attained on Shabbos through menuchah, so on the weekdays that same elevated level is reached through doing battle for the sake of Heaven.