Sahih al-Bukhari 693
Sahih al-Bukhari · Book 10: Call to Prayers (Adhaan) · A slave or a manumitted slave can lead the Salat (prayer)
Narrated Anas:
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 " .
The Prophet (ﷺ) said, "Listen and obey (your chief) even if an Ethiopian whose head is like a raisin were made your chief."