Learning from history

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 -

إِنَّ فِى ذَٰلِكَ لَعِبْرَةً لِّمَن يَخْشَىٰٓ

Indeed in that is a lesson [i.e., warning] for whoever would fear [Allāh].