Muwatta Malik, Book 56, Hadith 1823 (In-Book) ⓘ

Malik related to me from al-Walid ibn Abdullah ibn Sayyad that al-Muttalib ibn Abdullah ibn Hantab al-Makhzumi informed him that a man asked the Messenger of Allah, may Allah bless him and grant him peace, "What is backbiting?" The Messenger of Allah, may Allah bless him and grant him peace, said, "It is to mention about a man what he does not want to hear." He said, "Messenger of Allah! Even if it is true?" The Messenger of Allah, may Allah bless him and grant him peace, said, "If you utter something false, then it is slander."

حَدَّثَنِي مَالِكٌ، عَنِ الْوَلِيدِ بْنِ عَبْدِ اللَّهِ بْنِ صَيَّادٍ، أَنَّ الْمُطَّلِبَ بْنَ عَبْدِ اللَّهِ بْنِ حَنْطَبَ الْمَخْزُومِيَّ، أَخْبَرَهُ أَنَّ رَجُلاً سَأَلَ رَسُولَ اللَّهِ صلى الله عليه وسلم مَا الْغِيبَةُ فَقَالَ رَسُولُ اللَّهِ صلى الله عليه وسلم ‏"‏ أَنْ تَذْكُرَ مِنَ الْمَرْءِ مَا يَكْرَهُ أَنْ يَسْمَعَ ‏"‏ ‏.‏ قَالَ يَا رَسُولَ اللَّهِ وَإِنْ كَانَ حَقًّا قَالَ رَسُولُ اللَّهِ صلى الله عليه وسلم ‏"‏ إِذَا قُلْتَ بَاطِلاً فَذَلِكَ الْبُهْتَانُ ‏"‏ ‏.‏