Warning Against the People of Innovation

It was said to Imam Ahmad, "Is the man who fasts, prays, and performs i'tikaf more beloved to you, or the one who speaks out concerning the people of innovation (bid'ah)?" He said, "If this person fasts, prays, and performs i'tikaf, then this only benefits him. However, if he speaks out concerning the people of innovation (bid'ah), then this benefits the Muslims, and this is better."

(Majmu Fatawa 27/231)