When a person has the physical symptoms of the spiritual disease Tzara’at … he must call out: ‘[I am] Impure! [I am] Impure!’ (VaYikra 13:45).
The Gemara inquires why the Metzora (a person afflicted with Tzara’at) is required to call out at all and why use the double expression: ‘[I am] Impure! [I am] Impure!’? (Mo’ed Katan 5a).
The Gemara answers that one mention of ‘Impure’ is to notify people to stay away so they do not become contaminated. The other mention of ‘Impure’ is to inform the public to pray to God for his recovery. But why does the Metzora need others to pray on his behalf? Why can’t he just pray himself?
The classic cause for contracting this Tzara’at disease is the habitual speaking of Lashon Hara (Evil speech) (Rambam, Tumat Tzara’at 16:10). Lashon Hara essentially refers to non-constructive statements that are either derogatory or potentially harmful to a third party. The Zohar explains that God will not listen to the prayers of
habitual speakers of Lashon Hara.
That is why the Metzora needs others to pray for him. Deliberately looking for the faults, rather than the merits, of others and talking about them to one’s friends brings with it the horrific consequence that such people will not be listened to by God, however strongly they pray and cry out and however many other good qualities that they may have.
It is told that the Chafetz Chaim, who was famous for his care with speech and who composed several books on this matter, had an original way to protect himself from speaking or hearing any Lashon Hara. As a person entered his room to speak to him, he would immediately begin talking with him words of Torah and ethical improvement until the person left.
In this way, he ensured that the conversation would not drift into topics which involved talking about other people.