What afflicted you the day the two armies clashed was in accordance with God’s will, and to distinguish the believers.
وَما أَصٰبَكُم يَومَ التَقَى الجَمعانِ فَبِإِذنِ اللَّهِ وَلِيَعلَمَ المُؤمِنينَ
wa maa asaabakum yawmal taqal jam’aani fabi iznil laahi wa liya’lamal mu’mineen