It states (14:35) בבית לי נראה כנגע, "Something like a nega (tzaraas) has appeared to me in the house." The 'כ at the beginning of כנגע means that the man isn't telling the kohen that he saw a nega, rather that he saw something that appears like a nega.
Rashi explains, "Even a talmid chacham, who knows that it is definitely a nega, shall not make his statement using a decisive expression, saying, 'A nega has appeared to me.' He should say, 'Something like a nega has appeared to me.'"
What is the reason for this halachah? Why can't the person say, "I saw a nega. I saw tzaraas"?
Reb Chaim Vital zt'l answers that the tzaraas seen with physical eyes is only a reflection of the primary plague, which is deep within his neshamah. Therefore, one says, בבית לי נראה כנגע, "I saw something that appears like tzaraas...” but he didn’t see the primary tzaraas. The primary tzaraas is on the neshamah.
With this information, we understand that tzaraas can also be present in our times. It is a mistake to think that tzaraas don’t exist anymore. Although tzaraas doesn't exist in our times as a white mark on one's skin, it does exist in the realm of the soul.
Furthermore, the Chofetz Chaim zt’l writes (quoting early sefarim) that in our times, tzaraas doesn’t appear as a white mark on the skin or as a red blotch on one's clothing. Today, the mark of tzaraas is poverty. So, if a person wants to save himself from poverty, he should be cautious and not speak lashon hara.
The Gemara compares lashon hara to the three cardinal sins: idolatry, adultery, and murder.
The Or Hachaim HaKadosh (14:9) writes, "Nothing distances a person from his Creator like lashon hara." Yet, people aren't careful with it. The sefarim explain that every mitzvah has a mazal. Lashon hara has a poor mazal. People aren't cautious with it.
The Gemara (Shabbos 155:) teaches, דעניא לית מכלבא דעתיר ולית מכלבא, "There isn't anything poorer than a dog, and nothing wealthier than a pig." The Vilna Gaon zt'l explains that the Gemara hints at the wealthiest and poorest mitzvah. The richest and best-kept mitzvah is the prohibition of eating חזיר.
Rebbe Uri of Strelisk zy’a said, “When one desires to say something forbidden and he holds back, it's as though he fasted eighty-four days. Rebbe Aharon of Belz zy’a added, “And I say, nach un nach, un nach," which means that it’s like fasting for eighty-four days, and much, much more than that.
The poorest and least kept mitzvah is the prohibition of speaking lashon hara. (The dog represents lashon hara, as the Gemara says, “Whoever speaks lashon hara, it would be proper to throw him to the dogs.”)
Despite its severity, people aren’t as cautious as they should be with this prohibition.
The Beis HaLevi zt'l would often open his tabak pushkah (snuffbox) and immediately close it. One of his students was curious about this, so when he had the opportunity, he opened the snuffbox and he found the letters נ"שמ ו"שפ written inside. He asked the Beis HaLevi about this. The Beis HaLevi replied that they are roshei teivos for פיו שומר נפשו מצרות שומר ולשונו, "Someone who guards his tongue is protecting himself from troubles." The Beis HaLevi would open his snuffbox, read the message, and remember to be careful with his speech. You save yourself from much trouble when you are cautious with your speech.
