במדבר, פרק י״ט, פסוק י״א

After extensive instructions detailing how to prepare the ashes of the red heifer, their true purpose finally emerges. These ashes are specifically designated for purifying individuals who have come into direct contact with a human corpse [ביאור יש״ר, ברכת אשר על התורה].

The spiritual root of this impurity stems from the moment of death, when the Angel of Death casts a spiritual filth upon the body as the soul departs. However, this does not apply to completely righteous individuals who pass away by a divine "kiss" from God. Because the Angel of Death has no power over them, their souls remain pristine, and their physical bodies do not absorb or transmit this impurity [רקנאטי, שפתי כהן]. Fundamentally, there is a clear distinction between the physical remains and the essence of the person; the body once belonged to the individual, but it is not their actual soul [רש ר הירש].

This state of impurity only takes effect once actual death has occurred, entirely excluding someone who is dying or severely wounded [רלב״ג]. Furthermore, this profound level of impurity, which requires a lengthy purification process, is unique to humans and does not apply to animal remains [אבן עזרא, ביאור יש״ר]. The scope of human impurity is universal, applying to men and women, adults and children [רלב״ג], as well as Jews and non-Jews alike [אבן עזרא, ביאור יש״ר]. It extends to a miscarried fetus that did not complete its term [רלב״ג, צפנת פענח, רש ר הירש, אדרת אליהו, מלבי״ם], and even to tiny amounts of flesh or blood from the deceased [אדרת אליהו]. There is, however, a disagreement among commentators regarding blood, with differing views on whether the law specifically includes the blood of the dead as a source of impurity or intentionally excludes it [צפנת פענח, מלבי״ם].

Although one might logically assume that touching a body causes impurity—given that merely standing in the same room as a corpse has that effect—the law is stated explicitly. This is because legal rulings and punishments cannot be established based on logical deduction alone [חזקוני, מלבי״ם]. A human corpse is considered the most severe source of spiritual impurity. A person who touches it becomes a primary source of impurity for a full seven days, whereas someone who touches that newly impure person only remains impure until the evening [תורה תמימה]. This establishes that contact with death carries a severity equal to that of a leper, which was previously the only known condition requiring a seven-day purification period [ביאור יש״ר].

The ancient purification process has left a lasting mark on enduring traditions. The widespread custom of washing one's hands after returning from a funeral or a cemetery serves as a direct reminder of the sprinkling of the purifying waters mixed with the ashes. Additionally, the practice of plucking grass at a cemetery hints at the future resurrection of the dead, serving as a hopeful symbol that just as grass withers and eventually grows anew, so too will human life be restored [רבנו בחיי].