Illustrations paragraph 11
If one knows that the father-in-law’s home is immodest, one must tell this and one does not need to fulfill any of the above conditions. Even if one only heard it from other people, one must also tell. But one must be careful not to make it seem one knows this oneself but say, “I heard so and so.”
I wanted to mention more examples about workmen, hired people, and servants, but printing expenses and time restraints prevented this. However, the rule is: A person must be careful not to get involved in other people’s affairs unless he truly knows the situation and his intent is beneficial and not motivated by hatred. Also, one must ensure that nothing contravenes halachah as a result of what one says. Then Hashem will help one to not be trapped by the evil inclination, save him from error, and show him wonders of His Torah.