Hadith is integral to the Qur'an, since they are inseparably linked to each other. It is impossible to understand the Qur'an without reference to Hadith. The Qur'an is the message, and the Hadith is the explanation of the message by the Messenger himself. I mention the following points to clarify the issue:
1. The Qur'an makes it abundantly clear that the function of the Messenger is not merely that of a deliveryman who simply delivers the revelation from Allah to us. Rather, he has been entrusted with the most important task of explaining and illustrating the same. This is a point mentioned in a number of verses in the Qur'an:
[ And We have revealed unto thee the Remembrance that thou mayst explain to mankind that which hath been revealed for them, and that haply they may reflect.] (An-Nahl 16:44)
[And We have revealed the Scripture unto thee only that thou mayst explain unto them that wherein they differ, and (as) a guidance and a mercy for a people who believe.] (An-Nahl 16:64)
Therefore, Hadith explains, clarifies, and removes ambiguities about the Qur'an. Hence, once we reject the Hadith, we may never be able to figure out the whole meaning of the Qur'an.