Sahih Bukhari Volume 002, Book 014, Hadith Number 068.
Narated By Anas bin Malik : Allah's Apostle (p.b.u.h) offered the Fajr prayer when it was still dark, then he rode and said, 'Allah Akbar! Khaibar is ruined. When we approach near to a nation, the most unfortunate is the morning of those who have been warned." The people came out into the streets saying, "Muhammad and his army." Allah's Apostle vanquished them by force and their warriors were killed; the children and women were taken as captives. Safiya was taken by Dihya Al-Kalbi and later she belonged to Allah's Apostle go who married her and her Mahr was her manumission.