Abu Hurayra reported that the Prophet, may Allah bless him and grant him peace, said, "When two people revile each other, the responsibility for what they say rests on the first to speak as long as the one who wronged does not become excessive."  

عَنِ النَّبِيِّ ﷺ قَالَ الْمُسْتَبَّانِ مَا قَالاَ فَعَلَى الْبَادِئِ مَا لَمْ يَعْتَدِ الْمَظْلُومُ  

As 423, but from Anas.  

عَنِ النَّبِيِّ ﷺ قَالَ الْمُسْتَبَّانِ مَا قَالاَ فَعَلَى الْبَادِئِ حَتَّى يَعْتَدِيَ الْمَظْلُومُ  

The Prophet, may Allah bless him and grant him peace, said, "Do you know what calumny is?" They said, "No, Allah and His Messenger know best." He said, "Telling people what other people have said in order to create dissension between them."  

وَقَالَ النَّبِيُّ ﷺ أَتَدْرُونَ مَا الْعَضْهُ؟ قَالُوا اللَّهُ وَرَسُولُهُ أَعْلَمُ قَالَ نَقْلُ الْحَدِيثِ مِنْ بَعْضِ النَّاسِ إِلَى بَعْضٍ لِيُفْسِدُوا بَيْنَهُمْ  

The Prophet, may Allah bless him and grant him peace, said, "Allah Almighty revealed to me that you should be humble and that you should not wrong one another."  

وَقَالَ النَّبِيُّ ﷺ إِنَّ اللَّهَ عَزَّ وَجَلَّ أَوْحَى إِلَيَّ أَنْ تَوَاضَعُوا وَلاَ يَبْغِ بَعْضُكُمْ عَلَى بَعْضٍ