بِذَنْبِهِمْ

بِذَنْبِهِمْ is a phrase (شِبْهُ الجُمْلَةِ), a genitive particle followed by a possessed noun and a possessive noun

PhraseParticle / Noun / NounNounNoun Particle
شِبْهُ الجُمْلَةِجَارٌ وَمَجْرُوْرٌ وَهُوَ مُضَافٌ وَ مُضَافٌ إِلَيْهِمُضَافٌ إِلَيْهِاسْمٌ مَجْرُوْرٌ وَهُوَ مَضَافٌحَرْفُ جَرٍّ
PhraseCompoundPossessive PronounGenitive noun + Noun possessedParticle of pulling down
  
due to their sinبِذَنْبِهِمْ=هِمْ+ذَنْبِ+بِ
due to the sin of theirstheirsthe sin ofwith
Surah/Below is the only verse in the holy Quran containing the genitive particle and nominal compoundبِذَنْبِهِمْ
Verse
however, they denied him and killed itفَكَذَّبُوْهُ فَعَقَرُوْهَا
so, their Lord destroyed them due to their sinفَدَمْدَمَ عَلَيْهِم رَبُّهُمْ بِذَنْبِهِمْ
91-11and made them equal in destructionفَسَوَّاهَا