Sahih Bukhari
Holding Fast to the Quran and Sunnah
Volume: 009 / Book Number: 092 / Hadith Number: 382
Narrated 'Abdullah:
The best talk (speech) is Allah's Book 'Quran), 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).