وَمَا أَصَابَكُمْ يَوْمَ الْتَقَى الْجَمْعَانِ فَبِإِذْنِ اللَّهِ وَلِيَعْلَمَ الْمُؤْمِنِينَ ١٦٦

And the agony that hurt you on the day when the two armies clashed with each other came about (only) by Allah’s command. And (this happened) so that Allah establishes the identity of the believers, (3:166)