The Book on Government
وَحَدَّثَنَا أَبُو بَكْرِ بْنُ أَبِي شَيْبَةَ، حَدَّثَنَا وَكِيعُ بْنُ الْجَرَّاحِ، عَنْ شُعْبَةَ، بِهَذَا الإِسْنَادِ وَقَالَ عَبْدًا حَبَشِيًّا مُجَدَّعًا .In other versions of the above tradition, the wordings are" an Abyssinian slave." and" a maimed Abyssinian slave
From Sahih Muslim, whose reports the scholars accept as authentic.