كتاب البر والصلة والآداب
45
The Book of Virtue, Enjoining Good Manners, and Joining of the Ties of Kinship
(20)
Chapter: The Prohibition Of Backbiting
(20)
باب تَحْرِيمِ الْغِيبَةِ ‏‏

Abu Huraira reported Allah's Messenger (ﷺ) 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.
حَدَّثَنَا يَحْيَى بْنُ أَيُّوبَ، وَقُتَيْبَةُ، وَابْنُ، حُجْرٍ قَالُوا حَدَّثَنَا إِسْمَاعِيلُ، عَنِ الْعَلاَءِ، عَنْ أَبِيهِ، عَنْ أَبِي هُرَيْرَةَ، أَنَّ رَسُولَ اللَّهِ صلى الله عليه وسلم قَالَ ‏"‏ أَتَدْرُونَ مَا الْغِيبَةُ ‏"‏ ‏.‏ قَالُوا اللَّهُ وَرَسُولُهُ أَعْلَمُ ‏.‏ قَالَ ‏"‏ ذِكْرُكَ أَخَاكَ بِمَا يَكْرَهُ ‏"‏ ‏.‏ قِيلَ أَفَرَأَيْتَ إِنْ كَانَ فِي أَخِي مَا أَقُولُ قَالَ ‏"‏ إِنْ كَانَ فِيهِ مَا تَقُولُ فَقَدِ اغْتَبْتَهُ وَإِنْ لَمْ يَكُنْ فِيهِ فَقَدْ بَهَتَّهُ ‏"‏ ‏.‏
Reference : Sahih Muslim 2589
In-book reference : Book 45, Hadith 91
USC-MSA web (English) reference : Book 32, Hadith 6265
  (deprecated numbering scheme)