Be’er Mayim Chaim: We understand that the Torah incorporates many different readings in a single verse. It is plausible that our verse alludes to the process of teshuvah.
The reason for this ought to be apparent. When a person sins, the aveirah that he bears results in a kind of death, until he purges himself of it. Chazal make this explicit: “Evildoers are considered dead even while they are still physically alive.”2 At it spiritual core, death is not simply the absence of life, but is a kelipah named “death.” This kelipah – a spiritual structure seemingly devoid of any significant spiritual content – truly lacks real vitality, which is a function of spiritual worth and value. Possessing none of its own, this kelipah exists only through its flimsiest connection to ruchniyus, which is a consequence of Hashem’s presence on some level inhering in everything without exception.3
Chazal teach that every aveirah accompanies the one who committed it, staying with him on the way to the Day of Judgment. Specifically, the aveirah persists in the form of a kelipah that does not simply fall away. The chronic evildoer is laden with these kelipos through the legion of sins he has performed. He is coated and encrusted with so many of these death-kelipos that he can be considered dead himself. The consequences of this are two-fold. He becomes captive to the kelipos that surround him, and subservient to them. His life is therefore no longer his own. Moreover, he damages the way the spiritual worlds interact with our lower world. The kelipos that surround him are receptive to any spiritual nourishment. In effect, they draw away the Divine ohr sent to this world for positive purposes, and divert it to strengthen their negative existence.
Realizing how he has become mired in sin, and the calamitous effect this has had on him, body and soul, a would-be penitent has two chief options.
The first is Torah study, purely for the sake of Hashem, without any admixture of lesser intentions. When a person attaches himself to Torah, he has in effect attached himself to HKBH Himself. If the attachment is strong enough, he wrests himself away from the dominion of the kelipos, and enters into His domain.
The second is the full observance of Shabbos, in all its detail. Chazal testify5 that one who fully observes Shabbos is forgiven even for overt idolatry. The supernal kedushah of Shabbos that is made available from on high is so powerful that kelipos simply cannot attach themselves to it.
The reciprocal relationship between the ohr of Shabbos and the kelipos underlies our definition of prohibited melachah on Shabbos. All of those melachos are sourced in kelipos. Before Adam sinned, the earth produced its bounty without human effort. As a consequence of the first sin, the earth and its inhabitants were cursed with 39 curses. Each curse is related to a melachah. When the future tikkun comes about, the land of Israel will once again produce cakes and wool garments,6 i.e. without the assistance of human labor. The 39 melachos will have become irrelevant.
In this vein, we can reexamine our pesukim: “Whoever touches the dead body of any human being,” i.e. when a person has sinned, and therefore made strong contact with the death-kelipos, “He shall become tameh for seven days.” The seven are the seven lower sefiros, the sefiros of activity. All of them become not only defiled, but become conduits carrying Hashem’s ohr to dark places. “He shall purify himself with it on the third day and on the seventh day.” He can rid himself of his ghastly burden through the mitzvos of three and seven, i.e. the study of what the gemara7 calls a Torah of threes, and the observance of the laws of the seventh day. If he follows this formula, then “He shall become tahor.”
Sources: 1. Based on Be’er Mayim Chaim, Bamidbar 19:11
2. Berachos 18B
3. Without that connection, it could not exist.
4. Avodah Zarah 5A
5. Shabbos 118B
6. Shabbos 30B
7. Shabbos 88A