Ali Bin Abu Talib (Radiyallaahu `anhu) narrated that according to Allah’s Messenger (Sallallaahu `alayhi wa sallam) said:
“… If anyone introduces an innovation in the religion, he will be responsible for it. (Good or bad). If anyone introduces an innovation or gives shelter to a man who introduces an innovation (in the religion) he is cursed by Allah, by His angels and by all the people.”
Abu Dawud Book 39, Number 4515
Related: The Most Evil of Things Are Innovations In Religion.