The Messenger of Allāh (peace be upon him) said,

فَإِنَّهُ مَنْ يَعِشْ مِنْكُمْ فَسَيَرَى اخْتِلَافًا كَثِيرًا، فَعَلَيْكُمْ بِسُنَّتِي وَسُنَّةِ الْخُلَفَاءِ الرَّاشِدِينَ الْمَهْدِيينَ، عَضُّوا عَلَيْهَا بِالنَّوَاجِذِ، وَإِيَّاكُمْ وَمُحْدَثَاتِ الْأُمُورِ؛ فَإِنَّ كُلَّ بِدْعَةٍ ضَلَالَةٌ

“Verily he among you who lives long will see great controversy, so you must keep to my Sunnah and to the Sunnah of the rightly Guided Caliphs, those who guide to the right way. Cling to it stubbornly with your molar teeth. Beware of newly invented matters (in the religion), for verily every bid’ah (innovation) is misguidance.” 

[Tirmidhi, Ahmad, Abu Dawud / Authentic]