Abdullah bin Abbas reported,

A man from the Ansar insulted one of Abbas's forefathers who had died during the days of ignorance, so Abbas slapped him. The man's people came and said, "By Allah, we will surely slap him just as he slapped our man," and they put on their weapons.When news of this reached the Messenger of Allah ﷺ, he ascended the pulpit and said, "People, who among the inhabitants of the earth is most honored before Allah?"They replied, "You are."He said, "Abbas is part of me and I am part of him. Do not curse our dead, lest you cause harm to our living."The people then came and said, "Messenger of Allah, we seek refuge in Allah from your anger."

حدثني حجين بن المثنى حدثنا إسرائيل عن عبد الأعلى عن ابن جبير

عن ابن عباس

أن رجلا من الأنصار وقع في أب للعباس كان في الجاهلية فلطمه العباس فجاء قومه فقالوا والله لنلطمنه كما لطمه فلبسوا السلاح فبلغ ذلك رسول الله ﷺ فصعد المنبر فقال أيها الناس أي أهل الأرض أكرم على الله قالوا أنت قال فإن العباس مني وأنا منه فلا تسبوا موتانا فتؤذوا أحياءنا فجاء القوم فقالوا يا رسول الله نعوذ بالله من غضبك