Translation:Mikraot Gedolot/Psalms/50:20

Text
You sit, against your brother you speak; against a son of your mother you give slander.

Rashi
You sit

In the seat of insulters.

Against a son of your mother

With whom you have no logical argument and quarrel, for he does not inherit with you.

Slander

A derogatory thing; to push him away; a language of "he pushes him" (Numbers 35:20)