Is every one who is not upon the Sunnah not a Muslim?

Question:
May Allah reward you, Honorable Shaykh. This questioner says: We understood from you that one who is not upon the Sunnah is not a Muslim. Is this the case for every one who opposes the Sunnah, and in every issue?

Answer:
I did not say that. I did not say that every one who opposes the Sunnah is not a Muslim. I say that this varies. It varies. Some of it is such that one is not a Muslim if he opposes in creed, associates partners with Allah, calls upon other than Allah, or denies His names and attributes. This one is not a Muslim. But if he opposes the Sunnah in recommended matters or obligatory matters, this is considered misguidance, not disbelief. It is considered misguidance to the extent of it, and it is a religious innovation (bid'ah), and the warning applies to him. So do not take matters in a general sense. There must be a distinction in this matter. Yes, and this is what obligates the Muslim to seek knowledge, because he may take these texts at their apparent meaning and declare people disbelievers, without returning to the people of knowledge or to the evidence that explains, clarifies, and elucidates them, because he does not know or understand. Yes.