Parashas Chukas presents the most enigmatic and mysterious laws of the Torah: the laws pertaining to the preparation of the Red Heifer, the Para Adumah.
The intricate and multifarious details include the requirement that the Para Adumah be completely burnt to ash. The ashes are then used to spiritually purify those who become tameh, ritually impure, from contact with the dead.
The opening discussion among Chazal agrees that one must not even attempt to understand or explain the mysterious nature of a chok. A chok is a Divine mandate and should remain unquestioned. But the burning question perplexed even the wisest of Jews, King Shlomo (Yoma 14a): “…it is far from my understanding.”
This burning question centers on why the kohen who prepares the Cow himself becomes impure:
Metamei es hatehorim u’metaheres hatemei’im — making the spiritually pure impure, while purifying the impure.
Only a kohen may burn the Cow in the preparation of the Red Heifer (see Mishnah Parah 3:6–7).
The Baal HaTurim notes (Bamidbar 19:2) that the gematria of Para Adumah matches the gematria of al avon ha’egel, “for the sin of the Golden Calf.” He thus parallels the specific ritual elements of the Para Adumah: all serve as the tikun for the sin and the elements associated with the Golden Calf, the Egel HaZahav.