Allah Most High says in Quran:
"But no, by thy Lord, they can have no faith until they make thee judge in all disputes between them and find in their souls no resistance against thy decisions, but accept them with fullest conviction" (IV: 65).
In this noble verse Allah Most High, swearing by His Own August and Holy Being, says that none can initiate into bounds of faith unless he, relating all affairs, believes in Allah's judgement, and the judgement of the Eminent Prophet .
Briefly, a true believer is he who conscientiously believes the Holy Prophet Hadith to be instrumental in all affairs.
The implied order of the verse is that all prophetic order should be accepted manifestly and without constraint. Matters relate to believing in all the Hadith. Neither should one disagree in nor try to repel. After Allah's Book, nothing should be considered equal to Hadith and one should not repudiate them. Neither should one act against nor should have any question in admitting them. The Holy Prophet statement is: -
"I swear by that Being in Whose possession is my life, that none of you can be true believers until he submits his wish to the religion I have brought."