Abu NajihIrbaz bin Sarian relates that the Holy Messenger (peace and blessings of Allah be with him) delivered a moving speech which greatly moved us and sent a wave of fear into our hearts. We said to him that his sermon appears like the last advice, then tell us something more as advice; whereupon he said: I advise you to be afraid of Allah (because of the obligation to Allah) and to hear and obey even a slave who may be put in authority over you. Those of you who survive me will notice a lot of differences. It will be incumbent upon you to follow my Sunnah (practices) and the practices of my rightly guided successors (Caliphs) and hold fast with these precepts and traditions and beware of innovations and inventions in religion. Because every innovation leads to wrong path.
(Abu Dawood)
Here the Holy Messenger gives some guidelines to his followers. First, the fear of God is the most essential for a believer to have in the heart. It is the only thing that precludes a person from committing any wrong.
The Messenger ﷺlays emphasis on compliance of the orders of Ameer, be he a slave. But if the Ameer issues directions in conflict with the teachings of Islam and Sunnah, people are not required to follow his orders.
A believer is to mould his life into the Sunnah of the Messenger ﷺand if he does not find any guideline therefrom, he can take a cue from the life of the Rightly Guided Caliphs.