Then, when it descends in their courtyard, evil will be the morning for those who had been warned!means, when the punishment comes down to the place where they are, terrible will be the day of their punishment and destruction.As-Suddi said:فَإِذَا نَزَلَ بِسَاحَتِهِمْ (Then, when it descends in their courtyard), means, in their homes;فَسَاء صَبَاحُ الْمُنذَرِينَ (evil will be the morning for those who had been warned!) means, how terrible that morning will be for them.It was reported in the Two Sahihs that Anas, may Allah be pleased with him, said,"On the morning of Khyber, when the people came out with their tools (to go about their daily work) and saw the (Muslim) army, they went back and said, `Muhammad by Allah! Muhammad and the army!'The Prophet said:اللهُ أَكْبَرُ خَرِبَتْ خَيْبَرُ إِنَّا إِذَا نَزَلْنَا بِسَاحَةِ قَوْمٍ فَسَاءَ صَبَاحُ الْمُنْذَرِينAllahu Akbar! Khyber has been destroyed. Then, when it descends in the courtyard of any people, evil will be the morning for those who had been warned!"وَتَوَلَّ عَنْهُمْ حَتَّى حِينٍ