Sahih Bukhari Volume 004, Book 055, Hadith Number 597.
Narated By Abu Huraira : Allah's Apostle was asked, "Who is the most honorable amongst the people?" He replied, "The most Allah fearing." The people said, "We do not want to ask you about this." He said, "The most honorable person is Joseph, Allah's Prophet, the son of Allah's Prophet, the son of Allah's Prophet, the son of Allah's Khalil" The people said, 'We do not want to ask you about this." He said," Then you want to ask me about the origins of the Arabs? People are of various origins. The best in the pre-lslamic period are the best in Islam, provided they comprehend (the religious knowledge)."