In Al-Mahasin it is narrated that Murazem ibn Hakim quoted on the authority of Imam Sadiq (a.s)
“Whoever opposes the tradition of Muhammad (the Prophet) is an infidel.”
من كتاب المحاسن: عن مرازم بن حكيم قال
سمعت أبا عبد الله (عليه السلام) يقول: من خالف سنة محمد فقد كفر.
Similar narrations
Mishkāt al-Anwār #795Imam Sadiq (a.s) said: “Whoever opposes a tradition is an infidel.”
Al-Kāfi #207“Abu ‘Abdallah (a.s.) who has said, ‘Whoever disagrees with the book of Allah and the Sunnah of Prophet Muhammad (s.a.) he has certainly...