Quran 26:201 from Surah Ash-Shu'araa on Divine Marvels.
لَا يُؤۡمِنُونَ بِهِۦ حَتَّىٰ يَرَوُاْ ٱلۡعَذَابَ ٱلۡأَلِيمَ
English translation: Not they will believe in it until they see the punishment [the] painful
Transliteration: la yu'minuna bihi hatta yarawu al-'adhaba al-alima