נבול-פה

Through foul language comes adulation.

Someone who speaks foul language, it is certain that in his heart he thinks thoughts of sin. From the sin of foul language, troubles and [evil] decrees are renewed, and the young men of Israel die, G-d forbid, and orphans and widows cry out and are not answered.

One who defiles his speech, even if they have sealed for him a decree of seventy years for good, they reverse it to bad. Also, they deepen Hell for him. This also applies to one who hears [such speech] and remains silent.

More stringent is one who speaks verbally than the one who performs an action.