In Islam a Muslim Believer has to accept whatever decisions Allah ﷻ and His Prophet ﷺ has already made for them and they know better for the believers than the believers know whats better for themselves and that is the essence of Imaan (Islamic faith): "It is not for a believing man or a believing woman, when Allah and His Messenger have decided a matter, that they should [thereafter] have any choice about their affair." When Allah ﷻ says He has made a decision, and His Messenger has made a decision, then as believers we do not differ as that could impact our Imaan. In another verse of the Quran we are informed of the Prophet's status in relation to the Quran and how significant are his teachings: “Allah did confer a great favor on the Believers when He sent among them a Messenger from among themselves, who rehearses to them the Signs (Verses) of Allah, purifies them, instructs them in Scripture, and teaches them Wisdom, whereas previously they had been in plain error.” The words "purifies them", "instructs them in scripture", "teaches them wisdom" implies his teaching the Quran, living in accordance to the Quran, expressed in His Actions (Sunnah) and Words (Hadith) to those around him in the first instance, and then for all generations to come. Therefore any objection to the Prophetic teachings is an objection to the statements of Allah ﷻ in the Quran, that puts a question mark on our faith.
 Al Quran 33:36
 Al Quran 3:164
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.
Rasool Allah ﷺ said: “From Adam to me, Allah sent a hundred and twenty-four thousand Prophets, of whom three hundred and fifteen were Messengers (i.e. entrusted with a book).”  A simple difference between a prophet and a messenger is that the former was chosen for prophethood but not revealed a book while the latter was not only honored with prophethood but also received a divine message which his followers collected in a book format. Apparently the hadith seems to provide no more than a figure of Prophets & Messengers that lived in the past. But if we ponder closely over the wording and ask why more prophets than messengers, we actually learn a profound lesson. It helps us gain an understanding about the very institution of prophethood. If the role of a prophet was simply to deliver the book, as some misguided people tend to argue, there should have been as many books and messengers as the prophets! But the very fact that there have been many prophets without a book firmly establishes the need for real life examples is greater than books. Real life examples are absolutely necessary as they are the prime source of inspiration just as the saying "actions speak louder than words". Its just like I have a book with info & instructions but if I do not have a teacher to teach and practically show me how to implement those teachings then most likely I am bound to make tons of mistakes. In the case of Imaan (faith) which is a matter of hereafter we need to act with utmost care, as there's even more at stake than life or death, its a matter of eternal paradise or eternal hellfire.
Many Muslims don’t realize that the 1st chapter of the Quran i.e. Surah Fatiha which we recite 17 times a day (in 5 times salaah) has the following words in one of its verses: "Guide us to the straight path. The path of those on whom You have bestowed Your grace. Not the path of those who earned your wrath and niether of those who go astray”  Notice that Allah ﷻ did not instruct us to recite "Guide us to the path of book or Quran", no! In fact what He has instructed us to ask to be guided on the path of “Those upon whom you have bestowed Your Grace” obviously meaning that we are asking Allah ﷻ to provide us a model, a practical example. Thus what could be best than emulating the life of the best teacher and man to ever have walked on the face of this earth: "Indeed, in the Messenger of Allah you have an excellent example..." The Hadith and Sunnah literature in Islam was not just collected for historical record. What Muslims have collected is unprecedented science of knowledge which no other nation has of their Prophet. Its equivalent cannot be found in other religions. Hence the importance of this literature in the contemporary lives of the Muslims is greater than ever.
To understand how and why Allah ﷻ has declared in the Quran that Prophet Muhammad's example is the best for entire human race, please read this topic - Prophet Muhammad ﷺ: The Best Role Model For All
 Musnad Ahmad Hadith # 21257
 Al Quran 1:6–7
 Al Quran 33:21
"O you who believe, do not raise your voices above the Prophet’s, do not raise your voice when speaking to him as you do to one another, or your [good] deeds may be cancelled out without you knowing." 
From the inception of Islam, the Muslims have received knowledge mainly through 2 primary sources and those are Quran and Hadith/Sunnah. This knowledge has been given to us for learning and practicing, however there are certain guidelines that Quran, Prophetic example and the example of the Companions teaches us when dealing and handling such knowledge. In this age of technology where information lies on our fingertips we also come across many ahadith and the apparent wording of their text makes us doubtful and we ask questions like "why does this hadith seemingly contradicts the Quran?" or "why do we feel this hadith is not right?" The hadith that seemingly contradict the Quran or appear incorrect to some minds is not due to the errors that it carries, but due to the lack of understanding that the minds carry. One of the salaf (earliest Muslim generation) named Ibn Uyayna (r.a) said something extremely wise about hadith literature: “Hadith are a source of misguidance to those who do not take them from its people (muhadditheen)” Muhadditheen are scholars and experts who study and carry expertise in the ilm al hadith (sciences of prophetic traditions). This means that if individual minds were to study hadith without necessary knowledge and guidance from scholars, they might very well be misguided due to the apparent wording of the text even though its supposed to guide them. Just as if a Quranic verse about a particular subject were to be taken in isolation and all other verses related to that same subject were ignored, we can make grave errors in understanding the subject. Same applies towards understanding hadith that are recorded in several books. If we pick one and try to understand in isolation then there is a great chance of us misunderstanding the lesson being given, as we did not consult other books of tradition that might carry part of that same lesson. Additionally, each prophetic hadith has a background just as each verse of the Quran has a background of its revelation. In most cases the backgrounds need to be kept in mind when understanding any particular hadith. To prevent these sort of mistakes is why Allah ﷻ has advised the Muslims to consult the people of knowledge: "...So ask the people of remembrance (i.e. learned), if you do not know..." - "….If they referred it (i.e the knowledge) to the Messenger and those in authority among them (i.e. the scholars), those seeking its meaning would have found it out from them. If it were not for God’s bounty and mercy towards you, you would almost all have followed Satan."
 Al Quran 49:02
 Al Quran 16:43 - Al Quran 4:83
The Prophet ﷺ predicted hadith rejection
Narrated Al-Miqdam ibn Ma'dikarib (r.a) that the Prophet ﷺ said: “Beware! I have been given the Quran and something like it (i.e. Sunnah & Hadith), yet the time is coming when a man replete on his couch will say: Keep to the Qur'an; what you find in it to be permissible treat as permissible, and what you find in it to be prohibited treat as prohibited.” 
The prophetic hadith predicts the appearance of such persons among the Muslims who will openly reject the hadith and challenge them while sowing doubts in the hearts of others of their soundness. Such people have come to appear in our times who proudly refer to themselves as "Ahle Quran" i.e. the people of the Quran, a misleading term because they are not identified by affirming the Quran but by the rejection of hadith. If they were truly affirming the Quran then there is no dearth of ayahs in the Quran that explicitly say to "follow the Prophet" or "obey him" or "take whatever he gives’"etc. Therefore the correct term for them would be Munkareen e Hadith i.e. those who reject hadith or Hadith Rejecters.
Please note that these Hadith Rejecters are not one type, they are 3 main types. The flagship of misguided groups is that they are prone to further divisions. Khalid Baig, an Islamic writer from South Africa has divided them in to 3 Groups and explains each:
1. The first group holds that the job of the Prophet ﷺ was only to deliver the Quran. We are to follow only the Quran and nothing else, as were the Prophet's companions. Further, Hadith is not needed to understand the Quran, which is sufficient for providing guidance.
2. The second group holds that the Companions were required to follow the Prophet ﷺ but we are not as we're not the companions.
3. The third group holds that, in theory, we also have to follow Hadith but we did not receive Hadith through authentic sources and therefore we have to reject all Hadith collections.
How can this group hold the first position yet profess belief in the Quran while it clearly says: "And We have sent down unto You the Message so that you may explain clearly to mankind what was sent down to them, and so that they may give thought." "Allah did confer a great favour on the Believers when He sent among them a Messenger from among themselves, who rehearses unto them the Signs of Allah, purifies them, instructs them in Scripture, and teaches them Wisdom, whereas previously they had been in plain error." Verses like these clearly mentions words like "explain clearly", "instructing them in scripture" which anyone with common sense would agree as to be Prophets words and actions.
How can anyone hold the second group's position, limiting the Prophethood to 23 years, yet profess belief in the Quran, while it says: "We did not send you except as Mercy for entire universe." "And We have not sent you (O Mohammad) except as a giver of good news and a warner to all mankind." These 2 Verses mention that Prophet ﷺ was sent to all generations i.e. for the past, present and future generations, so if he was alive and explaining the early generation to whom he was sent then naturally for the upcoming generations would be his hadith or words as he himself would not be present, simple.
The Third group's position is that since they didn't receive the hadith then how can they follow it? This obviously is contradicting because the people who collected the Quran are the same people who collected hadith, hadith has come to us through the same channel as Quran i.e. Companions of the Prophet. Since Allah ﷻ has promised to protect the Quran (Al Quran 15:09) then if the same Allah orders us to 'Obey the Prophet' in the Quran, don't you think He would preserve sources of Prophetic words? After all who inspired the early Muslims to compile the Prophet’s words and actions in a systematic way through a branch of knowledge that we know today as science of hadith (ilm al hadith). This effort of their’s is unparalleled as compared to achievements of all other non-Muslim nations and their scholars. No doubt they could not have succeeded in it had it not been Allah’s will. It should be common sense for a Muslim believer.
How did Hadith Rejecters appear?
The hadith rejection concept was alien to the Muslims till about 150 years ago when Muslims were colonized. This was the first time that the majority of Muslim world came under domination of such powers that were secular in their approach towards everything, even education. When their way of life came to dominate the Muslim world amid the weakening of the Ottoman Empire then the new Muslim generation influenced by the way of life of the West was inspired to believe that the only way to have success in this world materially is by abandoning the traditional Islamic knowledge of their ancestors as the Western people have done of their’s after Renaissance. Hadith knowledge was seen as an obstacle by some modern Muslim thinkers inspired by secular philosophies. This led towards them promoting this theory that Muslims do not need hadith if they choose to be "developed". The efforts to reinterpret the Islamic texts led towards birth of many confusions among Muslims which are still observable. Hadith rejection is one of such confusions of which the Prophet ﷺ warned us more than 14 centuries ago.
 Sunan Abi Dawud 4604 - www.Sunnah.com
 Al Quran 16:44
 Al Quran 3:164
 Al Quran 21:107
 Al Quran 34:28