The Torah tells us that a metzora must sit alone outside the encampment in the desert. The simple meaning of this passuk is that he cannot interact with the the rest of Klan Yisroel who are ritually pure.
However, Chazal tell us that the metzorah cannot even sit with other metzorahs. The commentators explain that just as a metzora, which was a result of speaking lashon hara, caused disruption of relationships between people, so too he must sit alone, measure for measure.
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Rabbi Aharon Dovid Singer
Rosh Kollel, NMB Kollel
305-972-6508