Surah Al-Imran, ayah 166

3:166

وَمَآ أَصَٰبَكُمۡ يَوۡمَ ٱلۡتَقَى ٱلۡجَمۡعَانِ فَبِإِذۡنِ ٱللَّهِ وَلِيَعۡلَمَ ٱلۡمُؤۡمِنِينَ ١٦٦

Wamā asābakum yawmal-taqal-jam'āni fabi'idhnillāhi waliya'lamal-mu'minīn

And what struck you on the day the two armies met [at Uḥud] was by permission of Allāh that He might make evident the [true] believers