Parashat Parah is the third of four special parashiot that were instituted in order to remember the Beit Hamikdash and its practices. Parashat Parah is read from Chukat, the section of the Torah that deals with the Parah Adumah or Red Heifer. When the Beit Hamikdash was standing, every Jew would come to Yerushalayim in order to bring a Korban Pesach, a Passover Offering. One of the prerequisites for bringing this korban was spiritual purity. A person had to be cleansed from many types of spiritual impurity including tumat meit, the impurity associated with coming into contact with a corpse. The only way to achieve this purity was, and still is today, through the Parah Adumah, the sprinkling of special water made from the ashes of the red heifer. The nature of tumat meit makes it very likely that large segments of the population would have needed the special water of the Parah Adumah. Consequently, already in the times of the Beit Hamikdash it was established that Parashat Parah would be read before the month of Nissan as a reminder to the people that Pesach was coming and that they needed to purify themselves from tumat meit.
    There is much discussion among the halachic authorities as to whether the reading of Parashat Parah is an obligation from the Torah or from the Rabbis.  That’s the reason why many are careful to attend this Torah reading and make sure that they catch every word. 
    Any discussion of Parashat Parah would not be complete without mentioning the unique nature of the mitzvah of Parah Adumah itself. Those who are involved in the preparation of the ashes of the cow become ritually impure, while the sprinkling of the water with those same ashes actually removes ritual impurity. The Torah calls this a Chok, a mitzvah that we do not know the reason for. The Sefer Hachinuch writes that God explained the reason for this mitzvah only to Moshe alone on Har Sinai. God told Moshe that the reasoning behind this mitzvah is only going to be given to him and not to others. Indeed, when Shlomo Hamelech, King Solomon, whom the Rabbis refer to as the “Wisest of all men”, wrote out the reasons for every mitzvah in the Torah, he was successful with all of them except for Parah Adumah.
    The Mishnah tells us that there were only nine Parot Adumot in all of Jewish history. The first was prepared by Moshe in the midbar and its ashes lasted until the destruction of the first Beit Hamikdash. The second was prepared by Ezra at the beginning of the second Beit Hamikdash and its ashes lasted well into its tenure.  The next seven came and went and their ashes lasted until the final destruction of the second Beit Hamikdash.  The tenth Parah Adumah, it is said, will be prepared by the Melech Hamashiach, himself, may he come speedily in our days and usher in a time when these ashes will no longer be needed.