Abu Huraira (may Allah be pleased with him) narrated that the Messenger of Allah (peace and blessings be upon him) said: "You will find people (in good and bad) like mines of gold and silver; those who were the best among them in the pre-Islamic period are the best in Islam as well, provided they gain understanding of the religion."
Hadith Referenceمسند الإمام الشافعي / كتاب فضائل قريش وغيرهم وأبواب متفرقة / 1792
Hadith Takhrijاخرجه البخاري، المناقب، باب المناقب (3495) ، (3496) ومسلم ، فضائل الصحابة، باب خيار الناس (2526)۔