Sayyiduna Abu Dharr (may Allah be pleased with him) said: The Messenger of Allah (peace and blessings be upon him) commanded me "to hear and obey, even if the ruler over me is an Abyssinian slave with mutilated limbs."
Hadith Referenceالسنن الكبرى للبيهقي / كتاب قتال أهل البغي / 16768
It is narrated from Sayyiduna Mu'adh bin Jabal (may Allah be pleased with him) that the Messenger of Allah (peace and blessings be upon him) said: "O Mu'adh! Obey every ruler, pray behind every imam, and do not revile any of my Companions."
This (chain) is munqati' (broken) between Makhul and Mu'adh.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب قتال أهل البغي / 16769