"The Messenger of Allah ﷺ prayed Fajr on the day of Khaibar during the time it was still dark, when he was near the enemy. Then he attacked them and said: 'Allahu Akbar! Khaibar is destroyed!' Twice. 'Then, when it descends in their courtyard, evil will be the morning for those who had been warned!'" [1] [1] As-Saffat 37:177  

صَلَّى رَسُولُ اللَّهِ ﷺ يَوْمَ خَيْبَرَ صَلاَةَ الصُّبْحِ بِغَلَسٍ وَهُوَ قَرِيبٌ مِنْهُمْ فَأَغَارَ عَلَيْهِمْ وَقَالَ اللَّهُ أَكْبَرُ خَرِبَتْ خَيْبَرُ مَرَّتَيْنِ إِنَّا إِذَا نَزَلْنَا بِسَاحَةِ قَوْمٍ فَسَاءَ صَبَاحُ الْمُنْذَرِينَ