The Messenger of Allah (ﷺ) said, “Do you know what is backbiting?” They said, “Allah and His Messenger know best.” He (ﷺ) said, “When you mention your brother in a way that he dislikes.” It was said, “What if that which I mention exists in my brother?” He (ﷺ) replied, “If what you mention exists in him, then you committed backbiting against him. If what you mention does not exist in him, then you have slandered him.”
(Muslim)
