Beware of small innovations
Imâm al-Barbahârî (d.329H) - rahimahullâh - said:
Beware of small innovations, because they grow until they become large. This was the case with every innovation introduced into this Ummah. It began as something small, bearing resemblance to the truth, which is why those who entered into it were mislead and then were unable to leave it. So it grew and became the religion which they followed, and thus deviated from the Straight Path and left Islâm. And may Allâh have mercy upon you! Examine carefully the speech of everyone you hear from in you time particularly. So do not act in haste and do not enter into anything from it until you ask and see: Did any of the Companions of the Prophet sallallâhu ’alayhi wa sallam speak about it, or any of the Scholars? So if you find a narration from them about it, cling to it, do not go beyond it for anything and do not give precedence to anything over it and thus fall into the Fire.”
Kitâb Sharhus-Sunnah (nos.7-8) of al-Barbahârî.