divine punishment of rejectors

وَقَالَ ٱلَّذِىٓ ءَامَنَ يَـٰقَوْمِ إِنِّىٓ أَخَافُ عَلَيْكُم مِّثْلَ يَوْمِ ٱلْأَحْزَابِ

And he who believed said, "O my people, indeed I fear for you [a fate] like the day of the companies -