Q. It is widely mentioned that the red heifer is a chok or law without reason, so why does Rashi in Chukas write that it comes to clean up after the golden calf. Let the mother clean up the mess of her son. So there is a reason after all?

A. Moshe Rabbenu, the “Giver of the Torah,” set the standards not to deviate from the mitzvos given to us. A Sefer Torah missing even a part of the smallest detail of a letter is pasul. We humans, who cannot understand fully the true reason of any of the mitzvos, often tend to rationalize them with our own, often wrong ideas. As a result we find heterim and permissions, that can be utterly wrong and harmful. That is exactly what occurred at the greatest of all of our tragedies, the making of the eigel; we rationalized incorrectly. The Parah Aduma, provides the only answer, help and respite. The reason of the Parah Aduma,is that there is no reason. We just follow and do what Hashem wants us to do, without the need to understand the why. As opposed to Shlomo Hamelech, who did deviate and found his own heterim. Moshe Rabbenu was the sole and unique expert on following Hashem’s will to the smallest of details.
Horav Shlomo Miller’s Shlit’a opinion is that the chok without reason statement, may apply to other inherent difficulties of the Parah Aduma, such as why it purifies the impure while it defiles the pure, or the fact that behaving like a korban, it is brought outside of the Beis Hamikdash.

Rabbi A. Bartfeld as advised by Horav Shlomo Miller Shlit’a