It was narrated from Abu Dharr that he reached Rabadhah when the Iqamah for the prayer had already been given, and there was a slave leading them in prayer. It was said:
“This is Abu Dharr,” so he (the slave) started to move back. But Abu Dharr said: “My close friend (i.e., the Prophet ﷺ) told me to listen and obey, even if (the leader was) an Ethiopian slave with amputated limbs.”

حَدَّثَنَا مُحَمَّدُ بْنُ بَشَّارٍ، حَدَّثَنَا مُحَمَّدُ بْنُ جَعْفَرٍ، حَدَّثَنَا شُعْبَةُ، عَنْ أَبِي عِمْرَانَ الْجَوْنِيِّ، عَنْ عَبْدِ اللَّهِ بْنِ الصَّامِتِ، عَنْ أَبِي ذَرٍّ، أَنَّهُ انْتَهَى إِلَى الرَّبَذَةِ وَقَدْ أُقِيمَتِ الصَّلاَةُ فَإِذَا عَبْدٌ يَؤُمُّهُمْ فَقِيلَ هَذَا أَبُو ذَرٍّ . فَذَهَبَ يَتَأَخَّرُ فَقَالَ أَبُو ذَرٍّ أَوْصَانِي خَلِيلِي ﷺ أَنْ أَسْمَعَ وَأُطِيعَ وَإِنْ كَانَ عَبْدًا حَبَشِيًّا مُجَدَّعَ الأَطْرَافِ .