حِسَابَهُم

حِسَابَهُم is a phrase (شِبْهُ الجُمْلَةِ) consisting of a possessed noun and an attached, third-person, plural, possessive pronoun

PhraseNoun / NounNoun Noun
شِبْهُ الجُمْلَةِمُضَافٌ وَ مُضَافٌ إِلَيْهِمُضَافٌ إِلَيْهِمُضَافٌ
PhrasePossessive compoundPossessive noun/ownerNoun possessed/owned
their reckoningحِسَابَهُم=هُم+حِسَابَ
reckoning of theirstheirsreckoning of
Surah/Below is the only verse in the holy Quran containing the possessive nominal compoundحِسَابَهُم
Verse
88-26then verily for Us will be their reckoningثُمَّ إِنَّ عَلَيْنَا حِسَابَهُم