The grave is the place of burial, it also symbolize death or extinction of physical body with fire or any other means. The questioning or the trial of grave will take place. The details of this life in grave and how it is conducted are not well known [most likely spiritual in nature, because resurrection will take place on the Day of Judgement (Allah knows the best)]. It is only known that the faithfuls who have done well in this life, being devout and doing what God requires them to do will be in a happy state, while determined sinners will suffer what is termed as the “torment in the grave”. This is intermediate stage; final trial will take place on the Day of Judgment.
In biblical accounts (New Testament), the spirits of the dead, are placed in a state or abode called ‘Hades’, the place of waiting before judgement. It is mentioned as ‘Sheol’ in the Old Testament. The righteous and the wicked are separated, the blessed dead are in that part of ‘Hades’ called paradise (Luke;23:43). They are also said to be in Abraham’s bosom (Luke;16:22). The wicked are in state of torments in hell (Luke;16:23).
According to the Islamic traditions, there will be a trial after death called ‘The Trial of the Grave’, which involves questioning the deceased person by two angels; Munkir and Nakir, about his/her Lord, his/her religion, and his/her Prophet. There “Allah confirms those who believe with a firm saying, in the present life and the hereafter” (Qur’an;14:27). The believer will say: “Allah is my Lord, Islam is my religion, and Muhammad (peace be upon him) is my prophet.” The unbeliever or the hypocrite will say: “I do not know. I heard the people saying something and I said it.” The believers will be in a happy state in the grave; “Those whose lives the angels take in state of purity, saying ‘peace be on you; enter paradise for what you were doing’ (Qur’an;6:32).
The transgressing unbelievers will get the “torment in the grave.”: “If you could only see when the evildoers are in the agonies of death and the angels are stretching out their hands, saying, ‘Give up your souls! Today you shall be rewarded with the punishment of humiliation for what you used to say untrue about Allah, and for scornfully rejecting His signs”(Qur’an;6:93). The dead will rise as in a trance, and they will be confused in the new conditions! They will gradually regain their memory and their personality. They will be reminded that Allah in His grace and mercy had already announced the Hereafter in their probationary lives, and the word of Allah’s messengers, which then seemed so strange and remote, was true and was now being fulfilled! The new dreadful, frightening and terrifying environments will have such adverse affect that the period they had spent in the grave and the “torment in the grave” will appear to them as nothing, very short as if they were asleep :“And the trumpet is blown and lo! From the graves they will rush forth to their Lord! Crying: Woe upon us! Who hath raised us from our place of sleep? This is that which the Beneficent did promise, and the messengers spoke truth(Qur’an;36:51-52). The sayings of the Prophet are numerous and well-known in this subject.
A Muslim must believe in all that is reported in the Qur’an and the Prophetic Traditions concerning the (metaphysical) unseen matters (ghyeb). He should not contradict it by his worldly experience, because the affairs of the hereafter cannot be perceived by the affairs of this life. The difference between them is very great. Allah is the source of help.