12. It is forbidden to speak lashon hara about one Jew to another Jew, how much more so to a non-Jew. Besides for desecrating the honor of God and the honor of the Jewish people, the non-Jew will be quick to believe his words and publicize them, and he will thus cause hurt and damage to his fellow Jew. How much more so is it forbidden to inform on Jews to gentiles, for in such a case the informer is considered a heretic.
ט׳ באב ה׳תש״פ
Every moment that prerson restrain him mouth he acquiting to the Hidden Light, that there is no Mal'ach and creation to be able Imagine.(Hagra letter) 1