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 Exalted:
{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 - .... Ibn Habib said: Abu Ja'far narrated to us from Abu Jureij, from Ata, from Ibn Abbas, who said:
"Udd died, the father of Adnan, and Adnan, and Ma'ad, and Rabi'ah, and Mudar, and Qais Ghaylan, and Tamim, and Asad, and Dhubba, in Islam, following 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 they were Muslims following the religion of Ibrahim (peace be upon him)." And in the narration of al-Zubayr ibn Bakkar from the report of Maymun ibn Mihram,
from Ibn Abbas, who narrates it as a marfu' (elevated) statement: "Do not curse Mudar or Rabi'ah, 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."