Salams.
يُوۡفُوۡنَ بِالنَّذۡرِ وَيَخَافُوۡنَ يَوۡمًا كَانَ شَرُّهٗ مُسۡتَطِيۡرًا
'يُوۡفُوۡنَ بِالنَّذۡرِ' is 'historically' read as 'they fulfil their vows'. Why can't it be read as: 'they heeded to/took the warnings';considered Rabb's threats/warnings seriously?
Ok, I know this is 'unorthodox'; understand the seriousness of 'traditional/historical' readings/meanings and the consequence of immature, individual speculations. I do not know Arabic grammar, nor am I even qualified to 'disclose' my wild speculations; not to mention reading my شَّهَوَاتِ into the text/Rabb's Speech.
I also don't know if this is of your 'interest'/domain.
But still, ... 'from a structural/gramatical point of view', could, 'يُوۡفُوۡنَ بِالنَّذۡرِ' be read as 'they heeded/took the warnings'; And in this context, they took Rabb's threat seriously and feared that day of inevitable--لَأَمْلَأَنَّ جَهَنَّمَ مِنكَ--judgement?
جزاك اللهُ