Assalam alaikum,
The Messenger of Allah, Sallallahu alaihi Wasallam, said:--"Let me not find one of you, reclining on his couch, when he hears something regarding what I have commanded or forbidden saying: 'We do not know. What we found in Allah's Book we have followed'. (Abu Dawud)

This is a good reminder against today's casual attitude with which some Muslim, unfortunately, discard the Sunnah of our Prophet, may Allah bless him and grant him peace. Allah Subhanahu Wa Ta'ala repeatedly links obedience of Allah to obedience of His Messenger. Allah says, "And whoever obeys the Messenger, thereby obeys Allah"-(Qur'an 4:80) and "Whatever the Messenger gives you, take it and whatever he forbids you, refrain frm it".-(59:7)...there are many Ayats of the Qur'an itself condemning having a 'Qur'an only' approach.

To divorce the Sunnah from Islam is to render Islam ineffective...for example, the Qur'an directs us to pray, but without the Sunnah, how would we know how to pray?...or how to calclulate and give/pay the Zakkat?..