Sunan an-Nasa'i 4775

Ibn 'Abbad narrated that:a man slandered one of his forefathers from the time of the Jahiliyyah, and Al-'Abbas slapped him. His people came and said: "Let him slap him as he slapped him," and they prepared for quarrel. News of that reached the Prophet, and he ascended the Minbar and said: "O People, which of the people of the Earth do you know to be the most noble before Allah?" They said: "You." He said: "Al-Abbas belongs to me and I to him. Do not defame our dead or offend our living." Those people came and said: "O Messenger of Allah, we seek refuge with Allah from your anger; pray to give us