We're continuing in chapter one of the Chafetz Chaim’s sefer Ahavat Yisrael, talking about the negativity of Sinat Hinam/baseless hatred. He says, If we look deeply into this sin, we'll realize how detrimental it is, because it causes a spirit of contamination to come upon him. He continues, It's known that for every limb that a person does a Mitzvah with, a spirit of holiness rests upon that limb, and the opposite- If you do a sin, a spirit of contamination comes upon it. The source for the positive is Bamidbar 15,40
וַעֲשִׂיתֶ֖ם אֶת־כׇּל־מִצְוֺתָ֑י וִהְיִיתֶ֥ם קְדֹשִׁ֖ים לֵאלֹֽקיכֶֽם
Doing Mitzvot brings kedusha..And the opposite. This is true for every limb; If you listen to something improper with your ears, then a spirit of contamination goes on your ears, etc… This is true for individual limbs that a person's soul is not dependent on.They're not vital organs. Although no one wants to have a corrupted ear, you can survive without one.
But when this spirit of contamination goes onto a vital organ like the heart, then the person is spiritually dead. Therefore, he says, there is a tremendous detriment in the sin of baseless hatred, because the sin of baseless hatred is fundamentally in the heart, and therefore it brings a spirit of contamination on the heart.
And just as the heart is what pumps the blood into the whole body, your spiritual heart is what pumps spiritual blood throughout your body. Once the heart is contaminated, it pumps contamination into the entire body. That's why the sin of Sinat Hinam is so detrimental.
The Chafetz Chaim mentions this concept in his introduction to volume three of Mishna Berura on Hilchot Shabbat, where he explains why it’s so severe, that if one is transgresses Shabbat, he is considered not part of the Jewish people.
He says that Shabbat is all about our Emuna, our belief, and belief is a heart mitzvah. So when a person sins on Shabbat, it's has v’shalom like a heart attack. It's not like a person stubbed his toe. Certain sins are like when someone stubs his toe. No one wants to have a stubbed toe, but you could survive it. However, a heart attack, a brain attack, those are not things that one can survive. Therefore, Sinat Hinam is one of those vital organ sins, that one has to be so careful of.
Have a wonderful day.