﴿ حَتَّىٰٓ إِذَا بَلَغَ مَطْلِعَ ٱلشَّمْسِ وَجَدَهَا تَطْلُعُ عَلَىٰ قَوْمٍۢ لَّمْ نَجْعَل لَّهُم مِّن دُونِهَا سِتْرًۭا ﴾

“[And then he marched eastwards] till, when he came to the rising of the sun he found that it was rising on a people for whom We had provided no coverings against it:”

Please check ayah 18:91 for complete tafsir.