إِنَّ ذٰلِكَ لَحَقٌّ تَخاصُمُ أَهلِ النّارِ

That is indeed a true account: the contentions of the inmates of the fire.

EXEGESIS

Ahl (inmates) literally refers to a group that are united by something, like blood or creed.^{‎[1]Raghib, p. 96.} When someone has close affinity to something they can be called the ahl of that thing. So the people of Kufa, for example, could be called ahl al-kūfah. Here, the ahl al-nār means the people residing in the fire.  

EXPOSITION

This glimpse into the arguments and attitudes of the inmates of hell is drawn to a close with the declaration, That is indeed a true account: the contentions of the inmates of the fire. The word ḥaqq means that what was described is not only true but that it must be so, as in it is inevitable that they will have such an argument because of their divisive and petty nature.^{‎[2]Razi, 26/406; Mizan, 17/220.} Because of their self-centred conceit and egos, their friendships were situational and only ran skin-deep. Their friends of today will become their enemies in the hereafter.^{‎[3]Nemuneh, 19/327.}

[1] Raghib, p. 96.
[2] Razi, 26/406; Mizan, 17/220.
[3] Nemuneh, 19/327.