The Book on Government
وَحَدَّثَنَاهُ ابْنُ بَشَّارٍ، حَدَّثَنَا مُحَمَّدُ بْنُ جَعْفَرٍ، وَعَبْدُ الرَّحْمَنِ بْنُ مَهْدِيٍّ، عَنْ شُعْبَةَ، بِهَذَا الإِسْنَادِ وَقَالَ عَبْدًا حَبَشِيًّا .This hadith has been transmitted on the authority of Shu'ba with the same chain of transmitters, and he said:"An Abyssinian slave
From Sahih Muslim, whose reports the scholars accept as authentic.