Language:
كتاب الأذان
10  
Call to Prayers (Adhaan)
(54)
Chapter: A slave or a manumitted slave can lead the Salat (prayer)
(54)
باب إِمَامَةِ الْعَبْدِ وَالْمَوْلَى
Sahih al-Bukhari 693

Narrated Anas:

The Prophet (ﷺ) said, "Listen and obey (your chief) even if an Ethiopian whose head is like a raisin were made your chief."

حَدَّثَنَا مُحَمَّدُ بْنُ بَشَّارٍ، حَدَّثَنَا يَحْيَى، حَدَّثَنَا شُعْبَةُ، قَالَ حَدَّثَنِي أَبُو التَّيَّاحِ، عَنْ أَنَسٍ، عَنِ النَّبِيِّ صلى الله عليه وسلم قَالَ ‏ "‏ اسْمَعُوا وَأَطِيعُوا، وَإِنِ اسْتُعْمِلَ حَبَشِيٌّ كَأَنَّ رَأْسَهُ زَبِيبَةٌ ‏"‏‏.‏
Reference : Sahih al-Bukhari 693
In-book reference : Book 10, Hadith 88
USC-MSA web (English) reference : Vol. 1, Book 11, Hadith 662
  (deprecated numbering scheme)