As we inch toward Pesach, each Shabbos takes on a special character; one of these is Shabbos Parah. The Mitzvah of the פרה אדומה, the red calf, is perhaps the most difficult of all Mitzvos to understand. Rashi cites it as one of those Mitzvos that the nations of the world confront us with, and the Midrash identifies אדומה פרה as the one Mitzvah whose deeper understanding eluded even Shlomo HaMelech, who said "אחכמה והיא רחוקה ממני אמרתי" (קהלת ז':כ"ג), indicating his inability to master this area of knowledge. Nevertheless, there may be some aspects of this bizarre rite whose symbolic significance we can begin to reveal.
As the Kohein burns the פרה אדומה, preparing its ashes for sprinkling, he tosses into the fire a number of other items, specifically, עץ ארז, cedar wood, אזוב, hyssop, and שני תולעת, royal-red thread from a worm (במדבר י"ט:ו'). This odd assortment of items is actually found in the processing of another person, namely, the Metzora, when he is preparing to reenter the camp after his period of isolation (ויקרא י"ד:ד'). On the surface, it is not difficult to see what these two have in common. Both the ashes of the אדומה פרה and the sprinkling of the penitent Metzora are part of purification processes, in which an individual affected by serious טומאה is brought back from his separation. In the case of the Metzora, his טומאת צרעת, the impurity resulting from his condition, prevented him from entering the camp of the Jews; in the case of the טמא מת, whose impurity is generated by contact with a dead body, his טומאה blocked his ability to enter the precincts of the Mikdash and to participate in any Korbanos. The obvious question is, why is this collection of items (that is, the cedar wood, the hyssop and the royal-red thread) necessary for the purification of these individuals?
Interestingly, two of these items appear as a pair elsewhere in Tanach (מלכים א' ה':י"ג). The ארז and the אזוב are used in the description of Shlomo's wisdom - he understood all the plants from the mighty cedar of Lebanon to the lowly hyssop growing out of the wall. (The ארז and the תולעת שני were both used in the construction of the Beis HaMikdash, although they do not appear together explicitly.) Perhaps this pairing and the contrast set up between the two halves of this pair can be helpful in trying to derive some symbolic meaning in the פרה אדומה purification.
Although our understanding of טומאה and its causes is limited at best, it has been suggested that it is related to a loss of potential and our lack of appreciation of that loss. The classic example of טומאה, of course, is that brought about by contact with death. Being confronted by that ultimate loss of human potential, and realizing our lack of appreciation of the unfulfilled opportunities represented by that death, brings about ultimate טומאה. The contrast between the mighty cedar and the lowly hyssop represents the full range of possibilities placed before us. Were we to use our potential properly, we could become cedars. Should we squander the opportunity, we sink to the level of the hyssop, a growth that is not even rooted in the ground.
What about the תולעת שני - the scarlet colored thread? While the origin of the color is a תולעת - a lowly worm, it produces the royal scarlet color used in the Mishkan. Whereas the cedar and hyssop represent the range of possibilities, the תולעת שני is a model of how far we can go with even meager raw capabilities. As we emerge from our טומאה, we are reminded of the almost endless opportunities presented to us, of the fact that our lack of appreciation of those possibilities in the past brought about our טומאה in the first place, and of the almost limitless potential we each carry within us.