On the day the Tabernacle was inaugurated, the 1st of Nisan 2449, G‑d instructed Moses how to purify the Jewish people from ritual defilement contracted by contact with a human corpse. First, a perfectly red-haired cow must be slaughtered and burned to ashes. Then, a liquid solution is compounded out of spring water and the ashes of the cow. The ritually defiled person begins a seven-day count. A priest then sprinkles some of the red-cow ash-solution on the defiled person on the third and seventh days. The defiled person must then immerse himself in a ritual pool (mikveh) and wait until nightfall in order to complete the purification process.
Mercy and Selflessness
בַּיּוֹם הַשְּׁלִישִׁי וּבַיּוֹם הַשְּׁבִיעִי יִטְהָר וגו': (במדבר יט:יב)
On the third and seventh days [the defiled person] must purify himself. Numbers 19:12

In order to purify ourselves from the defilement of death – which in psychological terms means the paralysis caused by depression or deadness toward the spiritual dimension of life – we must invoke the third and seventh emotional attributes of the soul. The third emotion is pity and the seventh emotion is lowliness. When we feel the pain our Divine soul suffers from its constricted consciousness in the material world, we are aroused to rescue it by studying G‑d’s Torah and performing His commandments. When we are not egocentric, the flow of Divine life-force and vitality that should energize our lives is not blocked by our self-centered interests.1