Narrated `Abdullah:
During the Pre-lslamic period of ignorance if any tribe became great in number, we used to say, "Amira the children of so-and-so." Narrated Al-Humaidi: Sufyan narrated to us something and used the word 'Amira'.
USC-MSA web (English) reference: Vol. 6, Book 60, Hadith 234
Arabic reference: Book 65, Hadith 4711