Does Al-Qurtubi's Hadith mean that minority opinions—such as considering abandoning prayer as disbelief—are wrong? And does this generalize to all beliefs that contradict the majority opinion? And does this apply to creed and jurisprudence? And is the majority opinion considered an evidence in the Usul al-Fiqh (principles of Islamic jurisprudence) based on this Hadith?

Consensus (Ijma') is an established proof by the Qur'an and Sunnah (definition), as Allah says: (And whoever opposes the Messenger after guidance has become clear to him and follows other than the way of the believers - We will turn him to what he has turned to and admit him to Hell, and what a wretched destination.)

Whereas the قول الجمهور (opinion of the majority) or the majority is not a proof in itself. When there is a disagreement, the obligation is to refer back to the Qur'an and Sunnah, as there is no sound evidence for its authoritativeness.

As for the Hadith (definition) (فَعَلَيْكُمْ بِالسَّوَادِ الْأَعْظَمِ - adhere to the greatest majority), its chain of narration is weak. Even if it were authentic, it does not pertain to jurisprudential or creedal matters. Rather, it relates to pledging allegiance to the ruler and not revolting against him, in which case the allegiance of the people of knowledge and those through whom the objectives of the Imamate are fulfilled suffices.