The Prophet's Authority in Islam

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."[1] 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.”[2] 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.

References:

​[1] Al Quran 33:36

[2] Al Quran 3:164

[Courtesy of  Zaid Shah | Rizqan Kareem | Most Excellent Sustenance]