It is narrated from Anas and Abu Huraira (may Allah be pleased with them) that the Messenger of Allah (peace and blessings of Allah be upon him) said: "Of two people who abuse each other, the sinner is the one who starts it, as long as the oppressed does not retaliate with more than one insult for one." Narrated by Muslim.
Hadith Referenceمشكوة المصابيح / كتاب الآداب / 4818
Hadith Gradingالألبانی:صَحِيح | زبیر علی زئی:صحيح
Hadith Takhrij´تحقيق و تخريج: محدث العصر حافظ زبير على زئي رحمه الله` «رواه مسلم (2587/68)»