Sahih al-Bukhari 696
Sahih al-Bukhari · Book 10: Call to Prayers (Adhaan) · Offering prayers behind a man who is a victim of Al-Fitan (trials and affections) or a heretic.
Narrated Anas bin Malik:
حَدَّثَنَا مُحَمَّدُ بْنُ أَبَانَ ، حَدَّثَنَا غُنْدَرٌ ، عَنْ شُعْبَةَ ، عَنْ أَبِي التَّيَّاحِ ، أَنَّهُ سَمِعَ أَنَسَ بْنَ مَالِكٍ ، قَالَ النَّبِيُّ صلى الله عليه وسلم لأَبِي ذَرٍّ " اسْمَعْ وَأَطِعْ، وَلَوْ لِحَبَشِيٍّ كَأَنَّ رَأْسَهُ زَبِيبَةٌ " .
The Prophet (ﷺ) said to Abu-Dhar, "Listen and obey (your chief) even if he is an Ethiopian with a head like a raisin."