Remember what Hashem, your God, did to Miriam on the way when you left Egypt (Devarim 24:9)
Almost all of Tazria and most of Metzora are concerned with the intricate laws of tzora'as. Tzora'as afflicted people as a consequence of having spoken lashon hara. This is hinted to in Ki Seitzei, where the Torah warns us to be careful with respect to the laws of tzora'as and immediately thereafter to remember Miriam's punishment in the desert for speaking lashon hara about her brother Moshe. Miriam was immediately afflicted with tzora'as and forced to leave the encampment for seven days.
It seems paradoxical that the Torah chose to admonish us not to speak about the faults and shortcomings of others by reminding us of Miriam's sin.
During the entire time Miriam was afflicted, the nation did not travel. The whole nation waited for her as a consequence of the merit she accrued by waiting to see what would happen to her three-month old brother Moshe when she placed him into the Nile in a basket (Sotah 9b). Again we wonder: What benefit was it to Miriam to have the entire Jewish people delayed for her sake. Did that waiting not highlight the cause of her banishment? Would it not have been better for Miriam for the nation to proceed, unaware of her sin?
The answer is that Miriam did not sin. Her intentions in speaking about Moshe were completely well-intentioned, without any malice. She meant no harm to her beloved brother; nor did she cause Moshe any harm, or even ill-feeling. Despite this she was stricken with tzora'as. Her disease was not a punishment but rather the inevitable, natural result of lashon hara. Because she had not sinned, Moshe did not pray for forgiveness for Miriam - only that she be healed.
The command to remember Miriam does not denigrate her, for she committed no intentional sin. But we do learn from that act of rememberance the devastating effect of lashon hara, even when spoken unintentionally and without malice. Just as it makes no difference if one swallows poison intentionally or unintentionally, so, too, lashon hara devastates us, even when spoken without deliberate malice.
To highlight the intrinsic devastation wrought by lashon hara, it had to be crystal clear that Miriam did not sin and that her intentions were in fact pure. Miriam exhibited her love for Moshe when she waited anxiously to see what would happen to him. The waiting of the nation for her was a reminder of her earlier waiting and, at the same time, the proof that she had acted without malice towards Moshe. As Rambam in Hilchos Tumas Tzira'as (16:10) writes:
...Concerning this the Torah warns us to be careful with tzora'as and to remember what Hashem did to Miriam, as if to say: "Contemplate what happened to Miriam the Prophetess when she spoke against her brother' who was younger than her, whom she brought up on her lap and for whom she endangered herself when she saved him from the sea and whom she had no intention to harm. She erred only in comparing him to the other prophets and [Moshe] did not care about what she said because [he] was a very humble person and still was immediatelhy punished with tzora's...
There were two distinct aspects of the Mikdash which atoned for lashon hara. The Gemara (Zevachim 88b) relates that both the ketores (incense) and the me'il ( the garment of the Kohen Gadol from which bells and pomegranate-like ornaments hung) atoned for lashon hara.
The Gemara explains that the me'il atoned for the lashon hara spoken publicly and the ketores for the lashon hara betzina (literally hidden lashon hara). The latter is difficult to understand, however, since we learn of the ketores' ability to atone for the lashon hara from its use to stop the plague that broke out when the people blamed Moshe and Aharon for the deaths of Korach and his entourage. That lashon hara was public.
Perhaps, then, the Gemara is referring to two aspects of the damage caused by lashon hara. According to this understanding, public lashon hara refers to the harm done to the person that it was spoken against. Hidden lashon hara refers to the spiritual damage to the speaker of the lashon hora himself, the destruction of his neshama.
What, then, is that spiritual destruction, which is physically manifested by tzora'as? It is the power of speech that distinguishes man from all other creatures. The faculty of speech enables man to fulfill his purpose in the universe. Through speech man attaches himself to his Creator by learningand teaching Torah; through speech man addresses his Creator in prayer; through speech man crystallizes his thoughts, which in turn leads to action, as it says(Devarim 30:14), "for this mitzvah is close to you in your mouth and heart to do it;" and finally, it is speech that enables man to communicate with thers to unite in the communal service of the almighty.
When man uses his unique power of speech to unite the world in service of Hashem, he realizes his potential as the pinnacle of Creation. The Hebrew word for tongue, lashon, is related to lash, the process of mixing silids and liquids together. The tongue gakes the spiritual inner essence of the loul and expresses it in the physical realm - thereby mixing spiritual and physical together.
Utilizing the tongue for lashon hara, to degrade, to defile, to cause strife and dissension, divests man of the very essence of his distinction as a human being by corrupting his most exalted faculty. The Yerushalmi says that there are three sins for which man is punished in this world and in the next - immorality, murder and idolatry - and lashon hara is equal to all three. These three sins represent the destrution of man's physical, emotional and spiritual self. Lashon hara equals them all. For the totality of the human being is destroyed by the corruption of his ultimate distinction, his speech, Thus, one afflicted with lashon hara defiles like a corpse. He is banished from society and mourns himself, for the essence of his being has been negated.
AT the conclusion of shemonah Esrei we beseech Hashem, "My God, guard my tongue from evil and my lips from speaking deceitfully." After we have used our mouths for communicating with our creator, we can fully appreciate the calamity inherent in corrupting that same wondrous instrument by using it for lashon hara.
The laws of childbirth precede the laws of tzora'as. Man has the ability to be a partner in creation, to create a new being, or he can take his own body and divest it of tis Divine essence by speaking lashon hara. Both extremes are presenged. The choice is ours. That is the literal intent of the words of Chazal that life and death are in the hands of tha tongue.