Parshas Mitzora: Dubna Magid - As Fate Hangs On A Single Word
The halacha is that only a Kohen can declare a Nega to be Tamei. A Talmid Chochom who knows the halacha can give his opinion, but the tumah starts and ends with the declaration of the Kohen. Why?
The Dubna Magid (Iturei Torah) explains that the reason we commit the terrible crime of speaking Lashon Hara is because we don't understand the severity of it. After all what damage can our spoken word do? If we understood the gashmiyus and ruchniyus ramifications of our mere utterances we'd never dare speak lashon hara.
"Therefore," says the Dubno Magid, "we teach the Mitzora this lesson with the Kohen. His Nega and all the halachos do nothing to him. It is only with a single word from the Kohen's mouth that he is either spared the grave punishment of tzoraas and with a single word doomed to his bitter fate."