Originally answered on August 5, 2019 on Quora - In the Qur'an Allah says 'Obey Allah, obey the messenger'. Why did Allah use the term 'messenger' and not use the name of Muhammad?
This is because the official designation of ‘Messenger’ as opposed to ‘Muhammad’ carries importance with the listeners so they take his authority seriously especially when it comes to revelation & guidance. Such as when a country’s President addresses the nation and makes an important decision then they are informed through official channels that ‘President has made the decision’ and not ‘xyz has made a decision’ as then the decision is coming from his position of authority and not just his person so they follow what has been decided and realize its importance.
Knowing the importance attached to the ‘Messenger’ designation, we may now understand why Allah ﷻ separately mentioned ‘Obey Allah’ and ‘Obey the Messenger’ in the Quran, such as the following set of ayahs (Al Quran 4:59–65). They specifically indicate Prophet’s independent authority and Allah ﷻ, in His divine wisdom, chose to give him this authority because the Prophet ﷺ came not merely to deliver a message but also explain its details using his individual wisdom and practically live accordingly to it so Muslims will always have his example as a reference for religious (and non-religious) matters if and when they require:
(Al Quran 4:59–65) Believers! Obey Allah and obey the Messenger, and those from among you who are invested with authority; and then if you were to dispute among yourselves about anything refer it to Allah and the Messenger if you indeed believe in Allah and the Last Day; that is better and more commendable in the end….(O Messenger!) Have you not seen those who claim to believe in the Book which has been revealed to you and in the Books revealed before you, and yet desire to submit their disputes to the judgement of taghut (the Satanic authorities who decide independently of the Law of Allah)…(And tell them that) We never sent a Messenger but that he should be obeyed by the leave of Allah…But no, by your Lord, they cannot become true believers until they seek your arbitration in all matters on which they disagree among themselves, and then find not the least resistance in their hearts over what you have decided, and accept it in willing submission.
The set of ayahs from 4:59–65 and the highlighted parts indicate that Allah ﷻ approved Prophet Muhammad ﷺ authority to act independently because of his status as well as his importance as a Messenger in deciding matters required for the completion of Islam. Its compilation is found in the Hadith/Sunnah literature which holds authority after Quran.