Unchanging Decrees Bringing Purity
זאת חקת התורה
"This is the chok (statute) of the Torah" (Bamidbar 19:2).
The piece opens with the Torah's posuk introducing the parah adumah as a "chok," a decree whose rationale is hidden, setting the theme that some mitzvos lie beyond human reasoning.
שיש מצות שנקראו חוקים שאין להשיג טעמם כי המצות הם מול תרי"ג איברים וגידים
There are mitzvos that are called chukim (statutes) whose reason cannot be grasped, for the mitzvos correspond to the six hundred and thirteen limbs and sinews [of a person].
Chukim are mitzvos whose logic we cannot access, because the full system of mitzvos corresponds to the taryag (613) limbs and sinews of a person, a structure beyond rational explanation.
וכמו ביצירת האדם יש כמה אברים וגידים שאין נודע פעולתם בדרך הטבע רק כפי ציור הפנימי של האדם הם צריכין להיות כך
And just as in the formation of a person there are several limbs and sinews whose function is not known by way of nature, but rather, according to the inner design of the person, they need to be precisely as they are,
Just as a person's body has limbs and sinews whose purpose is not evident from a natural standpoint, yet which must be exactly so to fit his inner design, the mitzvos likewise carry a hidden necessity.
כמו כן במצות
so too it is with the mitzvos.
The very same principle that governs the mysterious parts of the body applies as well to the mitzvos.
ולכן נק' חוקים שהם רמזים ורשימות ממדריגה גבוה שא"י לבוא לידי התגלות
Therefore they are called chukim, for they are hints and impressions from an exalted level that cannot come into revelation.
They are called chukim because they are coded hints and impressions from a spiritual level so lofty that it can never fully come down into revealed understanding.
והם אינם מקבלים שינוי ולכן נקראו חוקים
And they are not subject to change, and therefore they are called chukim (from the root meaning that which is engraved and fixed).
Because these mitzvos derive from that fixed, unchanging source, they themselves are unchangeable, which is the deeper meaning of the word "chok" — something engraved and permanent.
ולכן יש בהם כח הטהרה כמ"ש מי יתן טהור מטמא לא אחד שהם בשורש האחדות לכן אין מקבלים שינוי
And therefore they possess the power of taharah (purification), as it is written, "Who can bring a pure thing out of an impure one? Is it not the One?" (Iyov 14:4) — for they are rooted in the source of Oneness, and therefore they are not subject to change.
Their rootedness in Hashem's absolute Oneness, which admits no change, is precisely what gives them the power to purify even what seems hopelessly impure, as the posuk in Iyov teaches that only the One can bring purity out of impurity.
ולפי שהאדם בטבע ומקבל שינוים אינו יכול להשיג טעמי פרה
And since a person is bound up in nature and is subject to changes, he cannot grasp the reasons of the parah (the Red Heifer).
A person, embedded in the ever-changing natural world, cannot comprehend the reasons behind the parah adumah, since he himself lacks the constancy that the mitzvah reflects.
ולפי שמשה רבינו ע"ה כתיב בי' משה משה בלי פסוק שלא נשתנה מתחלתו עד סופו
And since regarding Moshe Rabbeinu, peace be upon him, it is written "Moshe, Moshe" (Shemos 3:4) without a pause separating the two utterances — indicating that he did not change from his beginning until his end —
Moshe Rabbeinu was different: the doubled "Moshe, Moshe" with no pause between them hints at an unbroken, unchanging constancy throughout his entire life.
לכן לו נגלה טעמי פרה
therefore to him were revealed the reasons of the parah (the Red Heifer).
Because Moshe embodied that same changelessness as the chukim, he alone was granted the understanding of the reasons of the parah adumah.
וטהרת פרה מבחי' תשובה שהוא למעלה מבנין הטבע וע"י תשובה זוכין לטהרה כנ"ל:
And the taharah of the parah (the Red Heifer) stems from the aspect of teshuvah, which is above the structure of nature; and through teshuvah one merits taharah, as explained above.
The purifying power of the parah flows from teshuvah, which transcends the natural order; by returning to that supra-natural root, a person attains taharah, tying together the whole piece's theme that the unchanging source is the wellspring of purification.
Summary: The Sfas Emes explains why the parah adumah is the paradigm of a "chok," a mitzvah whose reason is inaccessible to human reasoning. Just as a person's body contains limbs and sinews whose function is hidden yet which are demanded by his inner design, the mitzvos correspond to the taryag limbs and derive from a level too exalted to come into revelation; this is why they are called chukim, a word denoting that which is engraved, fixed, and rooted in Hashem's unchanging Oneness. Precisely because they stem from that changeless source, they possess the power of taharah to purify even the impure, as the posuk in Iyov teaches. Ordinary people, immersed in the flux of nature, cannot grasp the logic of the parah, whereas Moshe Rabbeinu — whose doubled name signals an unbroken constancy from beginning to end — was granted that understanding. Ultimately the taharah of the parah flows from teshuvah, which transcends the structure of nature, so that by returning to one's unchanging root a person merits taharah.