Are matters of creed established only by definitive proof, and is belief not obligatory in what has been reported therein from Ahad (single-chain) narrations? And is the torment of the grave established by definitive or speculative proofs, and what is the ruling on one who denies it due to its mention in Ahad narrations while the verses are speculative in their indication?

An Ahad (single-narrator) hadith (definition) that meets the conditions of authenticity is a proof in all matters of religion, whether related to belief or practice.

The hadiths about the torment and bliss of the grave are mutawatir (mass-transmitted) from the Prophet, peace and blessings be upon him, and are a matter of consensus among Muslim scholars. The people of knowledge have unanimously agreed that the torment of the grave is real, and that the deceased will be in either bliss or torment, and that this affects both the soul and the body.

Reports have been mutawatir from the Messenger of Allah, peace and blessings be upon him, affirming the torment and bliss of the grave and the questioning by the two angels. It is obligatory to believe in the establishment of this and to have faith in it. Many scholars have transmitted the mutawatir nature of the hadiths about the torment of the grave and the obligation to believe in it.