Chafetz Chaim, Part One, The Prohibition Against Lashon Hara, Principle 4, Opening Comments

בִּכְלָל זֶה יְבֹאַר אִסּוּר לָשׁוֹן הָרָע מִבֵּין אָדָם למָּקוֹם. וְתִקּוּן עֵל חֵטְא זֶה, וּבוֹ י"ב סְעִיפִים. In this principle there will be explained the issur of lashon hara between man and his Maker, and the tikkun [correction] for this sin. It contains twelve sections.