Thou sittest and speakest against thy brother; thou slanderest thine own mother's son.
Thou sittest and speakest against thy brother. "Sittest" implies deliberate purpose; taking thy seat habitually with slanderers (Psalms 1:1): the climax of sin.
Thou slanderest thine own mother's son - Hebrew, thou givest a blow (namely, with the tongue) to, etc. This is preferable, to the Septuagint х skandalon (G4625)]; and Gesenius translates, 'thou puttest a stumbling-block' in his way, laying a snare for him. For the commandments of the second table of the decalogue are referred to, Psalms 50:18 - theft and adultery, in breach of the 7th and 8th; false witness and slander, in violation of the 9th (Psalms 50:19-20).