How is the punishment of the grave administered to those who died at sea, those whose bodies were cremated and scattered in various places, or those killed and consumed by wild animals? Since they do not have a grave in the traditional sense, how can there be a punishment of the grave for them?
When the punishment of the grave is mentioned, the reference to the burial site is made based on the majority case; one should not assume that the punishment takes place strictly within the soil. There are valid reasons for stating this.
Whether Muslim or non-Muslim, everyone will inevitably encounter the life of the grave. Numerous Hadiths state that non-Muslims, too, are subjected to punishment in the grave.(See Bukhari: 1207, 1252)
If we were to claim that only those buried in the ground undergo punishment in the grave, it would imply that the majority of non-Muslims are exempt from such punishment—simply because they are cremated rather than buried in the earth.
The notion that God—who punishes sinful Muslims in the grave—would not inflict similar punishment upon non-Muslims is inconsistent with His divine law and His justice.
لَعَلِّىْۤ اَعْمَلُ صَالِحًـا فِيْمَا تَرَكْتُؕ كَلَّا ؕ اِنَّهَا كَلِمَةٌ هُوَ قَآٮِٕلُهَاؕ وَمِنْ وَّرَآٮِٕهِمْ بَرْزَخٌ اِلٰى يَوْمِ يُبْعَثُوْنَ
When death finally comes to one of them, he will say, "My Lord! Send me back so that I may do good deeds regarding what I have left behind!" But no! It is merely a word that he utters; and behind them is a barrier until the Day they are resurrected.
(Al-Quran 23:100)
This verse implies that the punishment of the grave is an experience occurring within a realm hidden by a barrier (*barzakh*). It does not necessarily mean that the event must take place physically within the soil.
Consider a scenario where a wicked person is buried, years later, in the exact same spot where a righteous person was previously interred. If the punishment were to occur literally within that specific burial site, it would lead to conceptual confusion.
اَللّٰهُ يَتَوَفَّى الْاَنْفُسَ حِيْنَ مَوْتِهَا وَالَّتِىْ لَمْ تَمُتْ فِىْ مَنَامِهَا ۚ فَيُمْسِكُ الَّتِىْ قَضٰى عَلَيْهَا الْمَوْتَ وَ يُرْسِلُ الْاُخْرٰٓى اِلٰٓى اَجَلٍ مُّسَمًّى ؕ اِنَّ فِىْ ذٰ لِكَ لَاٰیٰتٍ لِّقَوْمٍ يَّتَفَكَّرُوْنَ
Allah takes the souls at the time of their death, and those that have not died, during their sleep. He retains the one for which He has decreed death and releases the other until an appointed term. Indeed, in that are signs for a people who reflect.(Al-Quran 39:42)
This verse clarifies that God holds all souls in His possession. If we understand that He bestows punishment or bliss upon those souls in a realm beyond our sensory perception, the concept that "no one can escape the life of the grave" holds true. It is true that the practices of offering *Salam* (greetings of peace) to graves and visiting them—as well as the Prophet (PBUH) splitting and planting a date palm frond at the burial site of two individuals undergoing punishment—imply that the punishment takes place at the very spot of burial.
However, if we conclude based on this that punishment occurs only within the soil, it would imply that non-Muslims might escape such punishment.
For those who are buried, the life of the grave is situated at the burial site. Yet, it is not difficult for the Almighty to ordain a different form of grave-life for those who are not buried.
Alternatively, God could establish the life of the grave for everyone in a realm other than this earthly world.
The Prophet (PBUH) may have planted the date palm fronds at the burial site simply because it served as a tangible marker. Regardless of the specific nature of this existence, there is no doubt that no one is exempt from the life of the grave.