It was narrated that Anas said: “The Messenger of Allah صلی اللہ علیہ وآلہ وسلم prayed Fajr on the day of Khaibar during the time that it was still dark, when he was near the enemy. Then he attacked them and said: ‘AIlahu Akbar! Khaibar is destroyed!’ Twice. ‘Then, when it descends in their courtyard, evil will be the morning for those who had been warned!” (Sahih)