Quran 18:86 from Surah Al-Kahf on Divine Marvels.
حَتَّىٰٓ إِذَا بَلَغَ مَغۡرِبَ ٱلشَّمۡسِ وَجَدَهَا تَغۡرُبُ فِي عَيۡنٍ حَمِئَةٖ وَوَجَدَ عِندَهَا قَوۡمٗاۖ قُلۡنَا يَٰذَا ٱلۡقَرۡنَيۡنِ إِمَّآ أَن تُعَذِّبَ وَإِمَّآ أَن تَتَّخِذَ فِيهِمۡ حُسۡنٗا
English translation: Until when he reached (the) setting place (of) the sun he found it setting in a spring (of) dark mud and he found near it a community We said O Dhul-qarnain O Dhul-qarnain Either [that] you punish or [that] you take [in] them (with) goodness
Transliteration: hatta idha balagha maghriba al-shamsi wajadaha taghrubu fi aynin hami-atin wawajada indaha qawman qul'na yadha al-qarnayni imma an tu'adhiba wa-imma an tattakhidha fihim hus'nan