Laws of Rechilus / 7: 3-4 (102)

3. It is forbidden to speak rechilus to the subject of the rechilus or to any of his relatives, even if they tell him that they won’t pass it on. This is so, because they too will be angered that someone spoke badly about their relative, which is a transgression of the sin of rechilus.

4. It is forbidden to speak rechilus to one Jew regarding another Jew, or to a non-Jew. One who speaks rechilus to a non-Jew, his sin is greater as it is more likely that it will cause harm or damage.