The hereafter is the Day of Resurrection, i.e. the day in which all of humankind will be raised to stand before God and be judged on their actions. God reminds us, “Do they not think that they will be called to account- on a mighty day-A Day when (all) mankind will stand before the Lord of the Worlds?” It is indeed a great day and one that God has sworn by, “I do call to witness the Resurrection Day.”
It is a day in which God will gather everyone’s remains and clothe our bones with flesh once again, so all bodies will return to their earthly state. Then God will give these bodies life. God reminds us that he is capable of this, “Does man think that We cannot assemble his bones?” God has also given us indications and signs for this day, “At length, when the sight is dazed, and the moon is buried in darkness, and the sun and moon are joined together, that Day will man say: ‘Where is the refuge?’ By no means! No place of safety!” He also says, “When the sky is rent asunder, And hearkens to (the Command of) its Lord, and it must needs (do so);-and when the earth is flattened out, and casts forth what is within it and becomes (clean) empty, And hearkens to (the Command of) its Lord,- and it must needs (do so);- (then will come Home the full reality).”
Based on these verses it is incumbent for every believer to have firm conviction in the final hour, the hour in which God calls forth those who are in their graves, “Again, on the Day of Judgment, will ye be raised up.” It is incumbent, therefore, to prepare for it with righteous deeds, “And fear the Day when you shall be brought back to God. Then shall every soul be paid what it earned, and none shall be dealt with unjustly.”
A Muslim is also obliged to believe in all that has come that describes this great event. This means that a Muslim should also believe in the unseen related to the final hour such as belief in heaven, hell, the final judgment, resurrection, the intermediate life one lives after death until judgment day called Barzakh, God says “…and behind them is a barrier until the Day they are resurrected.”(23/100)
One must also believe in the grave and the good and the bad that can occur in it. A Muslim must believe in this as it has come from the Shari‘a. At the same time, a Muslim should not concern himself with the details as for every world there are specific rules and realities governing it. We are in this worldly life and therefore we cannot imagine what other realms and worlds are like, such as the world of the spirit etc.
The scholars have differed on the pleasure and the torment of the grave; is it something that befalls the soul, the body, or both? The opinion of Ibn Hubayra and Imam al-Ghazali is that both the pleasure and torment of the grave are experienced by the soul only. However, the majority of Sunni scholars from both the theologians and the jurists are of the opinion that both the soul and the body experience the pleasure and torment of the grave.
Imam al-Nawawi has stated, “both pleasure and torment [in the grave] are experienced by the body itself, or part of it after the soul is placed back in it or a part of it.” Ibn Jarir is of the opinion that the deceased is tormented in their grave without the soul being placed back in it and they experience the pain without being alive.
This is what Muslims need to believe in regards to the Day of Judgment in general and God is most high and all knowledgeable.