قَوْلُهُ تَعَالَى: {وَلَا يَغْتَبْ بَعْضُكُمْ بَعْضًا} [الحجرات: 12]
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. (Using translation from Muslim 2589)
أَنَّ رَسُولَ اللهِ ﷺ قَالَ «أَتَدْرُونَ مَا الْغِيبَةُ» قَالُوا اللهُ وَرَسُولُهُ أَعْلَمُ قَالَ «ذِكْرُكَ أَخَاكَ بِمَا يَكْرَهُ» قِيلَ أَرَأَيْتَ إِنْ كَانَ فِي أَخِي مَا أَقُولُ؟ قَالَ «إِنْ كَانَ فِيهِ مَا تَقُولُ فَقَدِ اغْتَبْتَهُ وَإِنْ لَمْ يَكُنْ فِيهِ فَقَدْ بَهَتَّهُ»