The Prophet ﷺ said: The gravest sin is going to lengths in talking unjustly against a Muslim's honour, and it is a major sin to abuse twice for abusing once.
قَالَ رَسُولُ اللَّهِ ﷺ إِنَّ مِنْ أَكْبَرِ الْكَبَائِرِ اسْتِطَالَةَ الْمَرْءِ فِي عِرْضِ رَجُلٍ مُسْلِمٍ بِغَيْرِ حَقٍّ وَمِنَ الْكَبَائِرِ السَّبَّتَانِ بِالسَّبَّةِ