Quran 27:21 from Surah An-Naml on Divine Marvels.
لَأُعَذِّبَنَّهُۥ عَذَابٗا شَدِيدًا أَوۡ لَأَاْذۡبَحَنَّهُۥٓ أَوۡ لَيَأۡتِيَنِّي بِسُلۡطَٰنٖ مُّبِينٖ
English translation: I will surely punish him (with) a punishment severe or I will surely slaughter him unless he brings me a reason clear
Transliteration: la-u'adhibannahu adhaban shadidan aw laadh'bahannahu aw layatiyanni bisul'tanin mubinin