Musannaf Ibn Abi Shayba 36:342

Yazid ibn Harun narrated to us, he said: Hammad ibn Salamah informed us, from Thabit, from Anas, that the Prophet (peace and blessings of Allah be upon him) would not raid until it was morning, and he would listen; if he heard the call to prayer (adhan), he would refrain, and if he did not hear the call to prayer, he would raid. He said: He came to Khaybar, and they had come out of their fortresses and dispersed into their lands, with them were their baskets and their pickaxes. When they saw him, they said: "Muhammad and the army!" The Messenger of Allah (peace and blessings of Allah be upon him) said: "Allah is the Greatest! Khaybar is ruined. Indeed, when we descend into the courtyard of a people, evil is the morning of those who have been warned." He fought them until Allah granted him victory, and he divided the spoils. Safiyyah fell into the share of Dihyah al-Kalbi. It was said to the Messenger of Allah (peace and blessings of Allah be upon him): "A beautiful young woman has fallen into the share of Dihyah al-Kalbi." So the Messenger of Allah (peace and blessings of Allah be upon him) purchased her for seven heads [of livestock/slaves], and he sent her to Umm Sulaym to prepare her. He said: "And I do not know but that he said: 'And she should observe her waiting period (iddah) with her.'" When he wanted to depart, the people said: "We do not know if he has taken her as a concubine or married her." When he mounted, he veiled her and had her ride behind him. They proceeded until, when they drew near to Medina, they quickened their pace, as they used to do when they returned. When they drew near to Medina, the she-camel of the Messenger of Allah (peace and blessings of Allah be upon him) stumbled, and he fell, and she fell. The wives of the Prophet (peace and blessings of Allah be upon him) were looking, peering out, and they said: "May Allah distance the Jewess and crush her." So he veiled her and helped her up.