Al-Imām al-Barbahāri [may Allāh have mercy on him] said:

“He who opposes the Book [the _Qur’ān_] and the guidance and example of the Messenger of Allāh صَلَّى اللّٰهُ عَلَيْهِ وَسَلَّمَ [the _Sunnah_] is considered one who invents newly reprehensible invented ways [beliefs or action] in the religion, even if he possesses knowledge and books in abundance.”

Sharh us-Sunnah | Page 270 | Al-Imām al-Barbahāri [may Allāh have mercy on him]

Translation: Authentic Quotes