This Shabbat we read פרשת מצורע. Usually, תזריע-מצורע are read together, but because of this year being a leap year, they are read separately.
The major subject of the Parsha is צרעת, or leprosy. We use a play on words and say that מצורע is an acronym for מוציא שם רע, bringing a bad name on someone.
Leprosy was considered the ultimate punishment for לשון הרע, and using speech in a negative way. There is even a rabbinic quote that says that לשון הרע is worse than the three cardinal sins of idol worship, murder, and immorality.
The damage that comes from using speech in a negative way, is sometimes irreparable. Physical wounds can heel. But the pain that is caused from harsh words or insults, never come back.
This is the reason why the leper is quarantined from the camp. He caused divisiveness among individuals, and is not allowed to interact with people, until he is cured.
Although we no longer have the methods of purification as we did in Temple times, we must be careful to use speech only in a positive manner.