Hellfire is a temporal punishment for whoever enters it from the sinful believers

Q 16: In his last book that recently published: "Al-Nar Mustashfa (Hell is a Hospital)", he talks about Hell as if it is a hospital. He says that Allah's Mercy in the Hereafter will include the Kafirs (disbelievers). The writer says that interpreting the words "Child of Adam (humans)" in the Hadith from the Messenger of Allah (peace be upon him) in which he said, When a Child of Adam dies, their deeds come to an end, except three: Sadaqah Jariyah (ongoing charity), beneficial knowledge, or a pious child who prays for them (for the deceased). In reference to the Muslims only shows limited understanding and is unjust.

A: The Fire will be a temporary punishment for those Mu'mins (believers) who enter it due to having committed sins. As to the Kafirs, it will be an eternal punishment for them that they will not be able to leave. This is substantiated by the evidence given previously in the answers to Questions nos. 14 and 15. Therefore, likening the Fire to a hospital is wrong, because the Fire is a place of punishment for those who enter it, whereas a hospital is a place of mercy. Those who are ill enter hospitals to be looked after, to be fed healthy food, and to be treated in the hope that they will recover; they do not go into a hospital to be punished or tortured, rather to benefit from the treatments they offer and be cured.As to the meaning of the words "Child of Adam" in the Hadith quoted in the question, it refers to those who die as Muslims, not those who die as Kafirs, according to the evidence that show that the good deeds of someone who dies (Part No. 3; Page No. 492) as a Kafir will be erased, and they will not be rewarded for them in the Hereafter. In fact, they will only receive good things during their worldly life. Allah (Exalted be He) says: Surely, those who reject Faith (disbelieve in Allâh and in Muhammad صلى الله عليه وسلم) as being Allâh’s Messenger and in all that which he صلى الله عليه وسلم has brought from Allâh), neither their properties, nor their offspring will avail them aught against Allâh. They are the dwellers of the Fire, therein they will abide. (Tafsir At-Tabarî). The likeness of what they spend in this world is the likeness of a wind which is extremely cold; it struck the harvest of a people who did wrong against themselves and destroyed it, (i.e. the good deed of a person is only accepted if he is a monotheist and believes in all the Prophets of Allâh, including the Christ عليه السلام and Muhammad صلى الله عليه وسلم). Allâh wronged them not, but they wronged themselves. Allah (Exalted be He) also says: If then they answer you not, know then that it [the Revelation (this Qur’ân)] is sent down with the Knowledge of Allâh and that Lâ ilâha illa Huwa: (none has the right to be worshipped but He)! Will you then be Muslims (those who submit in Islâm)? Whosoever desires the life of the world and its glitter, to them We shall pay in full (the wages of) their deeds therein, and they will have no diminution therein. They are those for whom there is nothing in the Hereafter but Fire, and vain are the deeds they did therein. And of no effect is that which they used to do. And He (Exalted be He) says: The parable of those who disbelieved in their Lord is that their works are as ashes, on which the wind blows furiously on a stormy day; they shall not be able to get aught of what they have earned. That is the straying, far away (from the Right Path). And: On the Day when those who disbelieve (in the Oneness of Allâh - Islâmic Monotheism) will be exposed to the Fire (it will be said): "You received your good things in the life of the world, and you took your pleasure therein. Now this Day you shall be recompensed with a torment of humiliation, because you were arrogant in the land without a right, and because you used to rebel against Allâh’s Command (disobey Allâh). Also: And We shall turn to whatever deeds they (disbelievers, polytheists, sinners) did, and We shall make such deeds as scattered floating particles of dust. (Part No. 3; Page No. 493) This involves no injustice or oppression, because it is the individual who wronged themselves through their Kufr (disbelief), which erased their deeds, as stated by Allah, the Most-Just and the Most-Fair. This is not limited understanding, but enlightened insight and adherence to the clear guidance of the Shari`ah (Islamic law).May Allah grant us success. May peace and blessings be upon our Prophet Muhammad, his family, and Companions!