Sahih Muslim , Hadith 2587 ⓘ
Abu Huraira reported Allah's Messenger as saying: When two persons indulge in hurling (abuses) upon one another, it would be the first one who would be the sinner so long as the oppressed does not transgress the limits.
حَدَّثَنَا يَحْيَى بْنُ أَيُّوبَ، وَقُتَيْبَةُ، وَابْنُ، حُجْرٍ قَالُوا حَدَّثَنَا إِسْمَاعِيلُ، - يَعْنُونَ ابْنَ جَعْفَرٍ - عَنِ الْعَلاَءِ، عَنْ أَبِيهِ، عَنْ أَبِي هُرَيْرَةَ، أَنَّ رَسُولَ اللَّهِ صلى الله عليه وسلم قَالَ " الْمُسْتَبَّانِ مَا قَالاَ فَعَلَى الْبَادِئِ مَا لَمْ يَعْتَدِ الْمَظْلُومُ " .
also referenced under: Book 45, Hadith 89 (In-Book) & Book 32, Hadith 6263 (USC-MSA)