If Shimon tells Reuven’s wife that Levi spoke negatively of Reuven, Shimon has committed an act of rechilus. Though he has not repeated the story to Reuven himself, there is no doubt that Reuven’s wife will bear animosity towards Levi for having denigrated her husband. The Chofetz Chaim expands this concept to include all relatives, based on the assumption that relatives are protective of one another, and feel personally hurt when one of their members is attacked.
In the above case, had Shimon related the information to someone outside of Reuven’s family, he would have been guilty of loshon hora, not rechilus. In Be’er Mayim Chaim, the Chofetz Chaim presents a case where one would be permitted to relate the information to non-family members. Reuven and Levi are involved in a monetary disagreement. Levi mentioned to Shimon that he was convinced that he was right and that he would win the forthcoming din Torah (court case). If Shimon were to mention this to someone outside of Reuven’s family, it would not be loshon hora (assuming that nothing derogatory was said about Reuven). However, if repeated to a member of Reuven’s family it would be rechilus, since family members are inclined to be offended by the suggestion that Reuven is wrong.
The Chofetz Chaim then presents a case of a Jew who sets a non-Jew against a Jew. For example: A non-Jew purchased an item from Aharon. David tells the non-Jew, “He overcharged you.” The non-Jew feels cheated and may come to hate Aharon. The Chofetz Chaim sees this type of rechilus as particularly dangerous because it may cause the non-Jew to seek ways to harm Aharon for having taken advantage of him.
The Chofetz Chaim states: “Some people stumble frequently in this matter. They denigrate merchandise which a non-Jew purchased from a Jew, or they find fault with the work which a Jew did for a non-Jew. This can cause the Jew harm, and often can mean the ruination of his livelihood.”