The mitzvah of the Red Heifer (Parah Adumah) is the quintessential example of suprarational commandments — those with no logical explanation, known as chukim (statutes).
Rashi cites the Sages regarding this mitzvah: “Because Satan and the nations of the world taunt Israel, saying: ‘What is this commandment and what rationale is there for it?’ — therefore the Torah uses the term chukah (statute): ‘It is a decree from before Me; you have no permission to question it.’”
The Sages are precise in their language. At first glance, if one wishes to instruct someone to fulfill a commandment even when he does not understand it, the proper phrase would be: “You have no permission to refrain from doing it.” Yet here it says, “You have no permission to question it.” This implies that fulfilling the commandment is not enough — the person is also required not to question or challenge G-d’s command.
Action and Awareness
Indeed, “the main thing is the deed” — the primary element is the actual performance of the mitzvah. If someone concentrates on all the mystical intentions of tefillin but fails to physically place them on his arm and head — he has not fulfilled the mitzvah at all. In contrast, if he does physically don the tefillin, even without the intentions of the mitzvah — he has fulfilled the mitzvah.
However, G-d desires that the observance of mitzvot permeate the entire range of a person’s faculties and not remain confined to the faculty of action alone. All aspects of a person’s soul should participate in performing the mitzvah — speech, thought, emotions, intellect, and even the higher faculties of will and delight. When a person performs a mitzvah in this way, it is carried out with his whole being, not just by a part of him.
No Inner Doubt
When performing a suprarational mitzvah, it is possible for a person to fulfill it externally while internally questioning it — his intellect does not accept it and remains skeptical. Such observance, says the Torah, is incomplete. One must fulfill the mitzvah without questioning it at all.
There is an even more refined level: a fleeting thought of doubt may arise in one’s mind, and the person immediately pushes it away. Yet even this is not considered complete, because the goal is that the values of Torah and mitzvot should be so deeply embedded in a person’s soul that such thoughts of doubt never arise in the first place.
Simple Faith and Submission
The complete observance of suprarational mitzvot occurs when a Jew is so deeply infused with simple faith and acceptance of the yoke of Heaven, that this inner orientation drives him to fulfill G-d’s will with self-sacrifice and deep inner conviction — to the extent that no doubts or questions ever arise about the divine will.
This is G-d’s desire: that a Jew observe Torah and mitzvot not only through action but with all the faculties of his soul. For commandments that are understandable, the Jew should comprehend them and have intellectual awareness of them. And for those that transcend understanding, the Jew should recognize that G-d and His will are beyond human intellect — and thus, they must be fulfilled with absolute submission, with no room whatsoever for questioning.
(from the teachings of the Rebbe, Torat Menachem, vol. 33, translated from Sichat HaShevua)