Allah says:

[هَـذَا فَوْجٌ مُّقْتَحِمٌ مَّعَكُمْ لاَ مَرْحَباً بِهِمْ إِنَّهُمْ صَالُو النَّارِ ]

(This is a troop entering with you (in Hell), no welcome for them! Verily, they shall enter in the Fire!) Here Allah tells us what the people of Hell will say to one another. This is like the Ayah:

[كُلَّمَا دَخَلَتْ أُمَّةٌ لَّعَنَتْ أُخْتَهَا]

(Every time a new nation enters, it curses its sister nation (that went before)) (7:38), which means, instead of greeting one another, they will curse one another, accuse one another of being liars and reject one another. When a new group arrives, the keepers of Hell will say,

[هَـذَا فَوْجٌ مُّقْتَحِمٌ مَّعَكُمْ لاَ مَرْحَباً بِهِمْ إِنَّهُمْ صَالُو النَّارِ ]

(This is a troop entering with you (in Hell), no welcome for them! Verily, they shall enter in the Fire!) meaning, because they are of the people of Hell.

[قَالُواْ بَلْ أَنتُمْ لاَ مَرْحَباً بِكُمْ]

(Nay, you (too)! No welcome for you!) means, those who are coming in will say,

[بَلْ أَنتُمْ لاَ مَرْحَباً بِكُمْ أَنتُمْ قَدَّمْتُمُوهُ لَنَا]

(Nay, you (too)! No welcome for you! It is you who brought this upon us,) meaning, `you called us to that which led us to this fate.'

[فَبِئْسَ الْقَرَارُ]

(so evil is this place to stay in!) means, evil is this abode and this destination.

[قَالُواْ رَبَّنَا مَن قَدَّمَ لَنَا هَـذَا فَزِدْهُ عَذَاباً ضِعْفاً فِى النَّارِ ]

(They will say: "Our Lord! Whoever brought this upon us, add to him a double torment in the Fire!''). This is like the Ayah,

[قَالَتْ أُخْرَاهُمْ لاٍّولَـهُمْ رَبَّنَا هَـؤُلاءِ أَضَلُّونَا فَـَاتِهِمْ عَذَابًا ضِعْفًا مِّنَ النَّارِ قَالَ لِكُلٍّ ضِعْفٌ وَلَـكِن لاَّ تَعْلَمُونَ]

(The last of them will say to the first of them: "Our Lord! These misled us, so give them a double torment of the Fire.'' He will say: "For each one there is double (torment), but you know not.'') (7:38), which means that each of them will be punished as he deserves.

[وَقَالُواْ مَا لَنَا لاَ نَرَى رِجَالاً كُنَّا نَعُدُّهُمْ مِّنَ الاٌّشْرَارِ - أَتَّخَذْنَـهُمْ سِخْرِيّاً أَمْ زَاغَتْ عَنْهُمُ الأَبْصَـرُ ]

(And they will say: "What is the matter with us that we see not men whom we used to count among the bad ones Did we take them as an object of mockery, or have (our) eyes failed to perceive them'') Here Allah tells us that when they are in Hell, the disbelievers will notice that they do not see people who they thought were misguided, while they thought of themselves as believers. They will say, `why do we not see them with us in the Fire' Mujahid said, "This is what Abu Jahl will say; he will say, `what is the matter with me that I do not see Bilal and `Ammar and Suhayb and so-and-so...' This is an example; all the disbelievers are like this, they think that the believers will go to Hell, so when the disbelievers enter Hell, they will wonder why they do not see them there, and they will say,

[مَا لَنَا لاَ نَرَى رِجَالاً كُنَّا نَعُدُّهُمْ مِّنَ الاٌّشْرَارِأَتَّخَذْنَـهُمْ سِخْرِيّاً]

(What is the matter with us that we see not men whom we used to count among the bad ones Did we take them as an object of mockery,) means, in this world,

[أَمْ زَاغَتْ عَنْهُمُ الأَبْصَـرُ]

(or have (our) eyes failed to perceive them) means, they will try to console themselves with this wishful thinking, so they will say, perhaps they are here in Hell with us, but we have not laid eyes on them. Then they will find out that they (the believers) are in the lofty levels of Paradise, as Allah says:

[وَنَادَى أَصْحَـبُ الْجَنَّةِ أَصْحَـبَ النَّارِ أَن قَدْ وَجَدْنَا مَا وَعَدَنَا رَبُّنَا حَقًّا فَهَلْ وَجَدتُّم مَّا وَعَدَ رَبُّكُمْ حَقًّا قَالُواْ نَعَمْ فَأَذَّنَ مُؤَذِّنٌ بَيْنَهُمْ أَن لَّعْنَةُ اللَّهِ عَلَى الظَّـلِمِينَ ]

(And the dwellers of Paradise will call out to the dwellers of the Fire (saying): "We have indeed found true what our Lord had promised us; have you also found true what your Lord promised (warned)'' They shall say: "Yes.'' Then a crier will proclaim between them: "The curse of Allah is on the wrongdoers.'') until:

[ادْخُلُواْ الْجَنَّةَ لاَ خَوْفٌ عَلَيْكُمْ وَلاَ أَنتُمْ تَحْزَنُونَ]

(Enter Paradise, no fear shall be on you, nor shall you grieve.) (7:44-49)

[إِنَّ ذَلِكَ لَحَقٌّ تَخَاصُمُ أَهْلِ النَّارِ ]

(Verily, that is the very truth -- the mutual dispute of the people of the Fire!) means, `this that We have told you, O Muhammad, about the dispute among the people of Hell and their cursing one another, is true and there is no doubt concerning it.'

[قُلْ إِنَّمَآ أَنَاْ مُنذِرٌ وَمَا مِنْ إِلَـهٍ إِلاَّ اللَّهُ الْوَحِدُ الْقَهَّارُ - رَبُّ السَّمَـوَتِ وَالاٌّرْضِ وَمَا بَيْنَهُمَا الْعَزِيزُ الْغَفَّارُ - قُلْ هُوَ نَبَأٌ عَظِيمٌ - أَنتُمْ عَنْهُ مُعْرِضُونَ - مَا كَانَ لِىَ مِنْ عِلْمٍ بِالْمَـَلإِ الاٌّعْلَى إِذْ يَخْتَصِمُونَ - إِن يُوحَى إِلَىَّ إِلاَّ أَنَّمَآ أَنَاْ نَذِيرٌ مُّبِينٌ ]

(65. Say: "I am only a warner and there is no God (worthy of worship) except Allah the One, the Irresistible,'') (66. "The Lord of the heavens and the earth and all that is between them, the Almighty, the Oft-Forgiving.'') (67. Say: "That is a great news,'') (68. "From which you turn away!'') (69. "I had no knowledge of the chiefs (angels) on high when they were disputing and discussing.'') (70. "Only this has been revealed to me, that I am a plain warner.'')