Allah says about the Day of Decision -- and it is the Day of Judgement -- that it is at a fixed time, with a set appointment. Its time cannot be added to or decreased. No one knows its exact time except Allah. This is as Allah says,

وَمَا نُؤَخِّرُهُ إِلاَّ لاًّجَلٍ مَّعْدُودٍ

(And We delay it only for a term fixed.) (11:104)

يَوْمَ يُنفَخُ فِى الصُّورِ فَتَأْتُونَ أَفْوَاجاً

(The Day when the Trumpet will be blown, and you shall come forth in crowds.) Mujahid said, "Groups after groups." Ibn Jarir said, "This means that each nation will come with its Messenger. It is similar to Allah's statement,

يَوْمَ نَدْعُواْ كُلَّ أُنَاسٍ بِإِمَـمِهِمْ

(The Day when We shall call together all human beings with their Imam.) (17:71)" Al-Bukhari reported concerning the explanation of Allah's statement,

يَوْمَ يُنفَخُ فِى الصُّورِ فَتَأْتُونَ أَفْوَاجاً

(The Day when the Trumpet will be blown, and you shall come forth in crowds.) Abu Hurayrah said that the Messenger of Allah ﷺ said,

«مَا بَيْنَ النَّفْخَتَيْنِ أَرْبَعُون»

(That which is between the two blowings is forty.) Someone asked, "Is it forty days, O Abu Hurayrah" But he (Abu Hurayrah) refused to reply, saying "no comment." They then asked, "Is it forty months" But he (Abu Hurayrah) refused to reply, saying "no comment." They asked again, "Is it forty years" But he (Abu Hurayrah) refused to reply, saying "no comment." (Abu Hurayrah added:) "Then the Prophet went on to say,

«ثُمَّ يُنْزِلُ اللهُ مِنَ السَّمَاءِ مَاءً فَيَنْبُتُونَ كَمَا يَنْبُتُ الْبَقْلُ، لَيْسَ مِنَ الْإنْسَانِ شَيْءٌ إِلَّا يَبْلَى، إِلَّا عَظْمًا وَاحِدًا، وَهُوَ عَجْبُ الذَّنَبِ، وَمِنْهُ يُرَكَّبُ الْخَلْقُ يَوْمَ الْقِيَامَة»

(Then Allah will send down a rain from the sky and the dead body will sprout just as a green plant sprouts. Every part of the last person will deteriorate except for one bone, and it is the coccyx bone (tailbone). From it the creation will be assembled on the Day of Judgement.)"

وَفُتِحَتِ السَّمَآءُ فَكَانَتْ أَبْوَباً

(And the heaven shall be opened, and it will become as gates.) meaning, paths, and routes for the descending of the angels.

وَسُيِّرَتِ الْجِبَالُ فَكَانَتْ سَرَاباً

(And the mountains shall be moved away from their places and they will be as if they were a mirage.) This is similar to Allah's statement,

وَتَرَى الْجِبَالَ تَحْسَبُهَا جَامِدَةً وَهِىَ تَمُرُّ مَرَّ السَّحَابِ

(And you will see the mountains and think them solid, but they shall pass away as the passing away of the clouds.) (27:88) He also says,

وَتَكُونُ الْجِبَالُ كَالْعِهْنِ الْمَنفُوشِ

(And the mountain will be like carded wool.) (101:5) And Allah says here,

فَكَانَتْ سَرَاباً

(As if they were a mirage.) meaning, they appear to the one who looks at them as if they are something, but they are actually nothing. After this they will be completely removed. Nothing will be seen of them, and there will be neither base nor trace of them. This is as Allah says,

وَيَسْـَلُونَكَ عَنِ الْجِبَالِ فَقُلْ يَنسِفُهَا رَبِّى نَسْفاً - فَيَذَرُهَا قَاعاً صَفْصَفاً - لاَّ تَرَى فِيهَا عِوَجاً وَلا أَمْتاً

(And they ask you concerning the mountains, say: "My Lord will blast them and scatter them as particles of dust. Then He shall leave them as a level smooth plain. You will see therein nothing crooked or curved.") (20:105-107) And He says,

" وَيَوْمَ نُسَيِّرُ الْجِبَالَ وَتَرَى الاٌّرْضَ بَارِزَةً

(And the Day We shall cause the mountains to pass away, and you will see the earth as a leveled plain.) (18:47) Allah then says,

إِنَّ جَهَنَّمَ كَانَتْ مِرْصَاداً

(Truly, Hell is a place of ambush) meaning, it is waiting in preparation.

لِلطَّـغِينَ

(for the Taghun) These are the disobedient rejectors who oppose the Messengers.

مَـَاباً

(A dwelling place) meaning, a place of return, final destination, final outcome, and residence. Allah said,

لَّـبِثِينَ فِيهَآ أَحْقَاباً

(They will abide therein Ahqab.) meaning, they will remain in it for Ahqab, which is the plural of Huqb. Huqb means a period of time. Khalid bin Ma`dan said, "This Ayah, and the Ayah,

إِلاَّ مَا شَآءَ رَبُّكَ

except your Lord wills. )11:107( both refer to the people of Tawhل0d. Ibn Jar0r recorded this statement. Ibn Jar0r also recorded from Sa0lim that he heard Al-Hلasan being asked about Allah s statement,

لَّـبِثِينَ فِيهَآ أَحْقَاباً

(They will abide therein Ahqab) "In reference to Ahqab, it has no specific amount of time other than its general meaning of eternity in the Hellfire. However, they have mentioned that the Huqb is seventy years, and every day of it is like one thousand years according to your reckoning (in this life)." Sa`id reported from Qatadah that he said, "Allah says,

لَّـبِثِينَ فِيهَآ أَحْقَاباً

(They will abide therein Ahqab.) (78:23) And it is that which has no end to it. Whenever one era comes to an end, a new era follows it. It has been mentioned to us that the Huqb is eighty years." Ar-Rabi` bin Anas said,

لَّـبِثِينَ فِيهَآ أَحْقَاباً

(They will abide therein Ahqab) "No one knows how much time this Ahqab is, except for Allah, the Mighty and Sublime. It has been mentioned to us that one Huqb is eighty years, and the year is three hundred and sixty days, and each day is equivalent to one thousand years according to your reckoning (in this life)." Ibn Jarir has recorded both of these statements. Allah's statement:

لاَّ يَذُوقُونَ فِيهَا بَرْداً وَلاَ شَرَاباً

(Nothing cool shall they taste therein, nor any drink.) meaning, they will not find any coolness in Hell for their hearts, nor any good drink for them to partake of. Thus, Allah says,

إِلاَّ حَمِيماً وَغَسَّاقاً

(Except Hamim, and Ghassaq) Abu Al-`Aliyah said, "The Hamim has been made an exception to the coolness, and Ghassaq is the exception to the drink." This has also been said by Ar-Rabi` bin Anas. In reference to the Hamim, it is the heat that has reached its maximum temperature and point of boiling. The Ghassaq is gathered from the pus, sweat, tears, and wounds of the people of Hellfire. It is unbearably cold with an intolerable stench. May Allah save us from that by His beneficence and grace. Then He continues,

جَزَآءً وِفَـقاً

(An exact recompense.) meaning, that which will happen to them of this punishment is in accordance with their wicked deeds, which they were doing in this life. Mujahid, Qatadah, and others have said this. Then Allah said,

إِنَّهُمْ كَانُواْ لاَ يَرْجُونَ حِسَاباً

(For verily, they used not to look for a reckoning.) (78:27) meaning, they did not believe that there would be an abode in which they would be taken to account.

وَكَذَّبُواْ بِـَايَـتِنَا كِذَّاباً

(But they denied Our Ayat Kidhdhaba.) meaning, they used to deny the evidences of Allah and His proofs for His creation, which He revealed to His Messengers. So they met these proofs with rejection and obstinance. His statement,

كِذَّاباً

(Kidhdhaba) it means rejection, and it is considered a verbal noun that does not come from a verb. Allah said;

وَكُلَّ شَىْءٍ أَحْصَيْنَـهُ كِتَـباً

(And all things We have recorded in a Book.) meaning, `surely We know the deeds of all of the creatures, and We have written these deeds for them. We will reward them based upon this.' If their deeds were good then their reward will be good, and if their deeds were evil their reward will be evil. Allah then says,

فَذُوقُواْ فَلَن نَّزِيدَكُمْ إِلاَّ عَذَاباً

(So taste you. No increase shall We give you, except in torment.) This means that it will be said to the people of the Hellfire, "Taste that which you were in. We will never increase you in anything except torment according to its type (of sin), and something else similar to it." Qatadah reported from Abu Ayyub Al-Azdi, who reported from `Abdullah bin `Amr that he said, "Allah did not reveal any Ayah against the people of the Hellfire worse than this Ayah,

فَذُوقُواْ فَلَن نَّزِيدَكُمْ إِلاَّ عَذَاباً

(So taste you. No increase shall We give you, except in torment.)" Then he said, "They will continue increasing in torment forever."