(2) باب الاِقْتِدَاءِ بِسُنَنِ رَسُولِ اللَّهِ صلى الله عليه وسلم
Narrated `Abdullah:
The best talk (speech) is Allah's Book 'Qur'an), and the best way is the way of Muhammad, and the worst matters are the heresies (those new things which are introduced into the religion); and whatever you have been promised will surely come to pass, and you cannot escape (it).
Reference: Sahih al-Bukhari 7277
In-book reference: Book 96, Hadith 10
USC-MSA web (English) reference(deprecated numbering scheme): Vol. 9, Book 92, Hadith 382