DEUT376 "Beware lest you forget the Lord, your God". This is the prohibition against being conceited (Sotah 5a). One who ridicules others is generally motivated by a feeling of superiority. If he were aware of his own faults, he surely would not deprecate others. The Talmud (ibid.) equates arrogance with idolatry and states that whoever has this trait will not be privileged to be resurrected by tchiyas hamaisim. The gravity of the transgression is increased if the speaker elevates his own esteem through the medium of degrading someone else. Our Sages (Yerushalmi Chagigah 2:1) I have declared that such a person will lose his share in olam haboh.