The Prophet ﷺ said to Abu-Dhar, "Listen and obey (your chief) even if he is an Ethiopian with a head like a raisin." (Using translation from Bukhārī 696)
السيوطي ٣٢٢١a:
"اسْمَعْ، وأطِعْ، وَلَوْ لِحَبَشيٍّ كَأَنَّ رَأسَهُ زبيبَةٌ".