It is narrated from Sayyiduna Abu Talhah (may Allah be pleased with him) that when the Messenger of Allah (peace and blessings be upon him) attacked Khaybar early in the morning, the people of Khaybar had already set out for their fields with their spades and baskets. When they saw the Prophet of Allah (peace and blessings be upon him) with the army, they turned their backs and fled. The Messenger of Allah (peace and blessings be upon him) said: "Allahu Akbar, Allahu Akbar, Allahu Akbar! Khaybar is ruined. Indeed, when we descend upon the courtyard of a people, evil is the morning of those who were warned."
Hadith Referenceالمعجم الكبير للطبراني / باب الزاي / 4687