Sahih Muslim
The Book of Virtue, Good Manners and Joining of the Ties of Relationship (Kitab Al-Birr was-Salat-I-wal-Adab)
Book Number: 032 / Hadith Number: 6377
Abu Huraira narrated directly from Allah's Messenger (may peace be upon him) that he said: People are like mines of gold and silver; those who were excellent in Jahiliya (during the days of ignorance) are excellent In Islam, when they have, an understanding, and the souls are troops collected together and those who had a mutual familiarity amongst themselves in the store of prenatal existence would have affinity amongst them, (in this world also) and those who opposed one of them, would be at variance with one another.