Sayyiduna Abdullah (may Allah be pleased with him) says: "It is only a matter of two things: guidance and speech. The most truthful speech is the speech of Allah, and the best guidance is the guidance of Muhammad (peace and blessings be upon him). The worst of things are newly invented matters, every newly invented matter is an innovation, every innovation is misguidance, and every misguidance is in (leads to) the Fire."
Hadith Referenceالمعجم الكبير للطبراني / باب العين / 8489