How Those Who Invent Religious Matters Must Be Dealt With

Imām Ibn Taimiyyah, may Allāh have mercy on him, said:

The deviated people who invent religious matters [in Islam]—it is a [religious] obligation upon on every capable person to forbid them from these invented matters in the religion that mislead people, and to disparage anyone who [engages in] them. Then, if [that person] does not stop, [the alternative is that] he punish him [within his ability and authority] with what [that person] deserves according to Islamic law, […] the least of which is his abandoning him: he does not get near him nor mix with him until he repents and follows the Book and the Sunnah and the path with which Allāh sent His Messenger.

Jamiʿ Al-Masāʾil, vol. 1, p. 92.