One who bears tales about his friend transgresses the negative commandment of (Vayikra 19:16): "You shall not go talebearing among your people." It is a great sin and leads to the killing of many souls in Israel, for which reason it is followed by "You shall not stand by the blood of your neighbor." (viz. Rambam, Hilchoth Deoth 8). Go and see what resulted from the rechiluth of Doeg the Edomite [viz. I Samuel 21], because of which there was wiped out the entire city of Nov, the city of Cohanim. And this negative commandment which we have adduced is that which the Torah wrote explicitly for this issur. But aside from this, there are many other [relevant] negative and positive commandments, as explained above in the introduction.