Word by Word Analysis

ذَٰلِكَ بِأَنَّهُمْ قَالُوا۟ لَن تَمَسَّنَا ٱلنَّارُ إِلَّآ أَيَّامًا مَّعْدُودَٰتٍ ۖ وَغَرَّهُمْ فِى دِينِهِم مَّا كَانُوا۟ يَفْتَرُونَ 24

That is because they say, "Never will the Fire touch us except for [a few] numbered days," and [because] they were deluded in their religion by what they were inventing.