Shemiras Halashon Halachos
Opening to Hilchos Lashon Hara – Curses 1) The person speaking lashon hara transgresses the verse (Devarim 27:24), "Cursed be he who strikes his fellow in secret," which refers to lashon hara.
2) He also transgresses, "Cursed be he who misdirects a blind person in the road," which refers to someone who places an obstacle before a person so that he should stumble in transgression. Here too, he causes the listener to stumble in lashon hara.
3) If, heaven forefend, he generally disregards the prohibition against lashon hara, he transgresses the additional curse of (Devarim 27:26), "Cursed be he who does not uphold the words of this Torah to do them," which refers to someone who does not accept upon himself all the mitzvos of the Torah without exception.
4) If he, heaven forefend, speaks lashon hara about his father or mother, he transgresses the curse (Devarim 27:16), "Cursed be he who dishonors his father and mother."
There is a well-known statement in the Gemara (Shavuos 36a), "'Cursed' includes both a curse and excommunication." Therefore, a person who is not careful about observing lashon hara should be fearful for his soul lest he was excommunicated in heaven because of this.
Many other evil things are involved in this sin of lashon hara, such as the trait of cruelty, and the trait of anger, which is a severe sin. Also, a person sometimes comes to mockery and other evil traits.