Hadith No: 8
Al-Ayni - Umdat al-Qari Sharh Sahih al-Bukhari - Book of the Beginning of Creation - Chapter on the Statement of Allah, the Most High:
{O mankind, indeed We have created you from male and female and made you peoples and tribes that you may know one another} (Surah Al-Hujurat 49:13)
Volume: (16) - Page Number: (68)
[The text is lengthy, so only the relevant excerpt is provided here]
4 - ... And Ibn Habib said: Abu Ja'far narrated to us from Abu Jureij, from Ata, from Ibn Abbas, who said:
"Add, the father of Adnan, and Adnan, and Mudar, and Rabi'a, and Ma'ad, and Qays Aylan, and Tamim, and Asad, and Dabbah died in Islam, upon the religion of Ibrahim (peace be upon him), so do not mention them except as you would mention Muslims." - And from Sa'id ibn al-Musayyib: that the Messenger of Allah (peace be upon him and his holy progeny) said, "Do not curse Mudar, for he was a Muslim upon the religion of Ibrahim (peace be upon him)." Also, in al-Zubair ibn Bakkar's narration from the hadith of Maymun ibn Mahran,
from Ibn Abbas, who reports it from the Prophet: "Do not curse Mudar or Rabi'a, for they were both Muslims." And the Messenger of Allah (peace be upon him and his holy progeny) said:
"When people differ, the truth is with Mudar."