As the Mishkan (Sanctuary) is about to become operational, one last detail must be addressed: Aharon and his sons must go through a process whereby they will become kohanim (priests). In addition to various rituals that will prepare them for their new position, a seven-day period of confinement is commanded, during which time the initiates are not to leave the Mishkan. We might describe these days as the "cooling off" period necessary for the transition from civilian life to the holy life of the kohen, yet the specific duration of this period of confinement seems to contain allusions to other contexts.
At various junctures, the Jewish People as a whole, and specific, particular individuals, were commanded to undergo transformative preparatory rituals in order to achieve a new level of holiness or a more elevated spiritual status. However, only in certain cases was a full seven days mandated: In the case perhaps most germane to the topic at hand, the Torah tells us that the High Priest (Kohen Gadol) is also separated for seven days in preparation for Yom Kippur. He leaves his home, his wife and family, and spends seven days in a state of spiritual, intellectual and physical preparation for the crucial task he will perform on the Day of Atonement. Similarly, the kohen who is appointed to prepare the Red Heifer, the instrument through which the people achieve ritual cleansing after any contact with death, is also separated for seven days in preparation for his holy task. While we might argue that the common denominator of all three instances of separation is simply a dedication of time in preparation for an exalted task, there may be a much deeper, more intrinsic connection between them.
Each of these three instances - the Mishkan, Yom Kippur, and the Red Heifer - create spiritual healing. The Mishkan was built in order to create a place to which any and all in need of spiritual repair could turn. Yom Kippur was set aside for all time as the most efficacious day of the year for healing communal and personal sins. The purpose of the Red Heifer is to purify after contact with death, which creates a spiritual malady that only a spiritual process can heal. In each case, the Torah outlines rituals designed to bring man close to God. Apparently, in order to achieve this closeness, a seven-day separation from normal life is required. But why? Why the separation, and why is an entire week mandated for these particular processes?
Often, sin is the result of man pursing his basest impulses, eschewing the divine image within him, averting his gaze from God, and instead choosing to follow his animal instinct. This may not seem like a "choice"; it is not the result of careful contemplation but of "spontaneous combustion," of a momentary lapse of clear thinking in which impetuousness wins, consequences are not considered, implications and ramifications are ignored, resulting in sin - or death. For this reason, the process through which the kohen is readied for his task is not simply a waiting period. It is part of an intellectual and spiritual process of maturation, as it were, in which he is weaned from impulsive behavior.
An essential aspect of the kohen's service is kavanah - intent or directed thought. If the kohen misdirects his focus while performing the ritual, even if every possible detail of the prescribed rite is performed with absolute precision, the service is invalidated. The smallest stray thought of partaking of the offering at the wrong time or place, for example, nullifies the entire offering.
It is for this reason that a period of separation is mandated. It allows the kohen an opportunity to recalibrate, to gain control over his thoughts and, by extension, his actions. This "quarantine" limits his most basic distractions to a minimum, creating a sort of funnel through which he may concentrate his attention, focus and direct his thoughts, and take full control of his intellectual and spiritual capabilities in order to master the physical, instinctual parts of his personality.
Another instance where a seven-day period of preparation may be found involves Moshe's preparation to ascend Mount Sinai for an experience that would change the Jewish People, and in fact all of mankind. At Mount Sinai, the Jewish People come of age, as it were: At the moment the Torah is received, mankind achieves a new level of spiritual and intellectual maturity, a level that puts them in touch with their inner greatness, their inner divinity. From that moment hence, the Torah that will constitute the charter of the newly-born nation and its moral, ethical and legal code. From this point on, they will be held accountable for their actions and responsible for their personal and communal conduct, rather than being ruled by instinct or impulse. As their capacity to control their animal instincts develops, their souls change, grow, flourish. When they fail, as they inevitably do, sin - even death - can and must be cleansed, healed. Focus and equilibrium must be regained through the triumph of the soul over the body.
The rehabilitative process is a personal journey, but it is facilitated by the kohen. Like any mentor, the kohen must undergo this same process of spiritual redirection in order to be a useful and effective guide. Indeed, the kohen's journey takes the process one step further, teaching us that man has the capacity not only to abandon impetuous, instinctive behavior, but to transform it into a something new: instinctual behavior based on devotion and self-sacrifice. How else can we explain the behavior of Major Ro'i Klein, a soldier and scholar who, upon seeing a grenade hurled at the soldiers under his charge, commanded them to take cover as he jumped upon the grenade, taking the full impact of the blast? The last words on his lips were the Shma, the declaration of unwavering confidence in the unity of God and His unique relationship with the Jewish People. With the holiness of a Kohen Gadol, he knowingly plunged into the crucible in order to save others. Yes, he acted instinctively, impulsively - but his instincts were not those of base physical survival. He had achieved an elevated and purified level of instinct that others before him throughout our history had achieved, a dedication to God and to the Jewish People that are born of the focus and attention - through kavanah - to which we are all commanded to aspire. Each of us is capable of transforming our instincts, elevating them to the level of holiness.
For a more in-depth analysis see: http://arikahn.blogspot.co.il/2014/03/audio-and-essays-parashat-tzav.html
For Torah on Purim see: http://arikahn.blogspot.co.il/2014/02/torah-for-purim.html