Sahih Muslim Book - 45, Hadith - 6709

حَدَّثَنِي زُهَيْرُ بْنُ حَرْبٍ ، حَدَّثَنَا كَثِيرُ بْنُ هِشَامٍ ، حَدَّثَنَا جَعْفَرُ بْنُ بُرْقَانَ ، حَدَّثَنَا يَزِيدُ بْنُ الأَصَمِّ ، عَنْ أَبِي هُرَيْرَةَ ، بِحَدِيثٍ يَرْفَعُهُ ، قَالَ: النَّاسُ مَعَادِنُ كَمَعَادِنِ الْفِضَّةِ وَالذَّهَبِ ، خِيَارُهُمْ فِي الْجَاهِلِيَّةِ خِيَارُهُمْ فِي الإِسْلاَمِ إِذَا فَقُهُوا ، وَالأَرْوَاحُ جُنُودٌ مُجَنَّدَةٌ ، فَمَا تَعَارَفَ مِنْهَا ائْتَلَفَ ، وَمَا تَنَاكَرَ مِنْهَا اخْتَلَفَ.

It was narrated from Abu Hurairah in a Hadith which he attributed to the Prophet (s.a.w): "People are of different qualities like silver and gold; the best of them in the Jahiliyyah will be the best of them in Islam, if they attain the true understanding of religion (Fiqh ). And souls are like conscripted soldiers; those whom they recognize they come together, and those whom they do not recognize, they stay away."