The idea that Munkar and Nakir question the newly buried dead about their faith belongs entirely to hadith literature and subsequent theological development, since the Qur'an does not name these two angels or describe this specific interrogation. The broader doctrine they serve, punishment or reward in the grave prior to the final resurrection, was itself a genuine point of theological contention within early and medieval Islamic thought rather than a point every school accepted without question.
Rationalist theological currents, most notably strands of Mu'tazilite thought, are recorded by later heresiographers as having questioned or reinterpreted aspects of grave punishment doctrine on the grounds that it sat uneasily with their broader theological commitments, while the Sunni theological mainstream that eventually became dominant affirmed the doctrine, including the questioning by Munkar and Nakir, as a fixed part of correct belief. The names, appearance, and precise procedure described for the two angels also show variation across different hadith collections and later manuals of belief, consistent with a doctrine that was elaborated gradually through generations of scholarly transmission and debate rather than delivered once in a single fixed and universally agreed form, even though it became, and remains, standard teaching in mainstream Sunni and Shia belief alike.