Hilchos Lashon Hara, Opening – Negative commands (5)

The speaker also breaks the negative commandment (Devarim 8:11), "Be careful lest you forget Hashem your G-d," which forbids arrogance. When he makes fun of another person, he probably sees himself as wise and important. If he saw his own faults, he would not make fun of others.

Chazal (our sages) say in Sotah (4b) that arrogance is a very serious sin. A person who has it will not rise at the resurrection of the dead. He is considered like an idol worshipper, the Divine Presence cries over him, and he is called an abomination.

This is especially true if the speaker of lashon hara makes himself look good by putting the other person down. Then he surely breaks this negative commandment. And the sages also say he loses his share in the World to Come: "Someone who is glorified through the calumny of his fellow has no portion in the world to come" (Yerushalmi, Chagigah 2:1).