Sahih Muslim · Hadith 6758
The Book of Virtue; Good Manners and Joining of the Ties of Relationship - كتاب البر والصلة والآداب
حدثنا يحيى بن أيوب، وقتيبة، وابن، حجر قالوا حدثنا إسماعيل، عن العلاء، عن أبيه، عن أبي هريرة، أن رسول الله صلى الله عليه وسلم قال " أتدرون ما الغيبة " . قالوا الله ورسوله أعلم . قال " ذكرك أخاك بما يكره " . قيل أفرأيت إن كان في أخي ما أقول قال " إن كان فيه ما تقول فقد اغتبته وإن لم يكن فيه فقد بهته " .
Abu Huraira reported Allah's Messenger (may peace be upon him) as saying: Do you know what is backbiting? They (the Companions) said: Allah and His Messenger know best. Thereupon he (the Holy Prophet) said: Backbiting implies your talking about your brother in a manner which he does not like. It was said to him: What is your opinion about this that if I actually find (that failing) in my brother which I made a mention of? He said: If (that failing) is actually found (in him) what you assert, you in fact backbited him, and if that is not in him it is a slander.
Gradings are classical jarḥ-wa-taʿdīl, name-matched to a rijāl index (not individually re-verified).