Is the punishment of the grave established in the Holy Quran, or is it restricted to the Prophetic Sunnah only? And how is one punished if they were never buried?

Some raise questions regarding the extent to which the punishment of the grave is established in the Holy Qur’an. The truth is that this concept is established with certainty in the two forms of revelation: the Book and the Sunnah, and it is among the fundamentals of faith in the Unseen (al-Ghayb) upon which the People of Sunnah and the Community (Ahl al-Sunnah wa al-Jama'ah) have reached a consensus.

First: The Authority of the Prophetic Sunnah

It is not a prerequisite for Sharia rulings or metaphysical truths to be detailed in the Holy Qur’an alone; the Prophetic Sunnah is a divine revelation that complements and clarifies what is in the Book. Numerous Hadiths have been transmitted from the Prophet ﷺ establishing both the punishment and the bliss of the grave through mass-transmission (tawatur).

As for the Hadiths regarding the punishment of the grave, they are many and mutawatir (mass-transmitted) from the Prophet ﷺ.

— Shaykh al-Islam Ibn Taymiyyah (Majmu’ al-Fatawa, 4/285)

Among these is what was narrated in the Sahihayn, such as his ﷺ statement regarding two graves: "They are being punished, and they are not being punished for something difficult to avoid" (Al-Bukhari), and his command to seek refuge from four things, including the punishment of the grave, in every prayer.

Second: Evidence for the Punishment of the Grave from the Holy Qur’an

The Holy Qur’an has alluded to the punishment of the Barzakh (the interval between death and resurrection) in several places, including the Almighty's statement regarding the people of Pharaoh:

{The Fire, they are exposed to it morning and evening. And the Day the Hour appears [it will be said], "Make the people of Pharaoh enter the severest punishment."}

[Surah Ghafir: 46]

This exposure to the Fire occurs in the Barzakh before the onset of the Hour. Likewise, the Almighty says: {And indeed, for those who have wronged is a punishment before that, but most of them do not know} [At-Tur: 47].

Third: The Punishment of the Grave and the Realm of the Unseen

As for those who wonder about the state of one who was not buried—such as one eaten by predators or drowned in the seas—the punishment does not pertain solely to the physical location (the grave), but rather it is a state that afflicts the soul and the body in the realm of Barzakh. Every person deserving of punishment will receive their share whether they are placed in the earth or not, because the laws of the Realm of the Unseen differ from our narrow material calculations.