"This is the law when a man dies in a tent," we read in this week's Torah portion, Chukat.

"This is the law when a man dies in a tent," we read in this week's Torah portion, Chukat. "Everyone who comes into the tent...and every open [earthen] vessel on which there is not a closely fitting cover, is [spiritually] unclean." Moreover, whatever substance was within the open vessel is also rendered spiritually unclean.
However, as explained by Maimonides, if a person happened to be in the tent of the deceased "in a sealed barrel with a 'closely fitting cover,'
" he remained spiritually pure and unaffected.
Every aspect of Torah provides us with a practical lesson to be applied in our daily lives. To the Jew, spiritual life and death are defined by his connection to G-d, as the Torah states, "And you who cleave unto G-d are all alive this day." Conversely, any weakening in our service of G-d or defect in that connection constitutes the Jew's spiritual death, G-d forbid.
Nonetheless, no matter how connected to G-d the individual Jew may be, he still exists within the context of the material world, defined as "a world in which the wicked are ascendant."
Therefore, no matter how "alive" the Jew is in absolute terms, the world around him is unclean; the Jew is always "in the tent of the deceased."
This is especially true during the exile, when darkness covers the face of the earth, in contradistinction to the times of the Holy Temple, when G-d's Presence in the world was openly perceived, thus enabling Jews to perform mitzvot with vitality and enthusiasm.
What can a Jew do to protect himself from negative influences during these last few minutes of exile? How can we guard ourselves against the spiritual uncleanliness that surrounds us "in the tent of the deceased"?
The answer lies in the above-mentioned ruling, on the principle that properly sealing an earthen vessel protects its contents from spiritual impurity.
In terms of our service of G-d, the Jew must strive for the humility and self-nullification symbolized by the earthen vessel, which is composed of the dust of the earth.
Our Patriarch Abraham epitomized this quality when he declared, "I am but dust and ashes"; similarly, we recite during the High Holidays, "Man, whose basic element is dust ...is likened to a shard of clay."
Every Jew is obligated, therefore, to fit himself with "a closely fitting cover" - to guard every opening and channel that connects him with the outside world in order to filter out the bad influences from the good. Doing so will protect him from spiritual uncleanliness and ensure that his connection to G-d remains healthy and intact.
Adapted from Likutei Sichot of the Rebbe, Vol. 23