Ali 'Imran 166

وَمَآ أَصَـٰبَكُمْ يَوْمَ ٱلْتَقَى ٱلْجَمْعَانِ فَبِإِذْنِ ٱللَّهِ وَلِيَعْلَمَ ٱلْمُؤْمِنِينَ

wamā aṣābakum yawma l-taqā l-jamʿāni fabi-idh'ni l-lahi waliyaʿlama l-mu'minīna

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