How does one respond to those who object to the independent legal reasoning (ijtihad) of the Companions and reject the authority of the Sunnah in establishing the torment and bliss of the grave, claiming that the Quran does not mention it, and considering the interpretations of the Companions to be fallible human endeavors?

This answer clarifies that one of the greatest means of refuting those who deny the Sunnah is to demonstrate its authoritativeness and the danger of denying it, citing Quranic verses and Prophetic hadiths that affirm the obligation of adhering to what the Messenger of Allah, peace and blessings be upon him, brought. It also emphasizes that the consensus of the Companions is a definitive proof that cannot be denied, especially in matters of the unseen, such as the torment of the grave. It mentions that denying what the Companions agreed upon may amount to disbelief according to some scholars. It reviews the sayings of the imams regarding the authoritativeness of the Companions' consensus, and that the torment and bliss of the grave are mutawatir (transmitted by multiple independent chains of narration) and have been agreed upon by scholars, and that denying it is an innovation and may amount to disbelief.