Musnad Ahmad 448:8

Ya'qub narrated to us, he said: My father narrated to us, from Ibn Ishaq, he said: Yazid ibn Abi Habib narrated to me, from Abu Marzuq, the freed slave of Tujib, from Hanash al-San'ani, who said: We went on a military expedition with Ruwayfi' ibn Thabit al-Ansari to a village among the villages of the Maghrib called Jarba. He stood among us as a preacher and said: "O people, I do not say to you anything except what I heard the Messenger of Allah (peace and blessings of Allah be upon him) say. He stood among us on the day of Hunayn and said: 'It is not lawful for a man who believes in Allah and the Last Day to water his water upon the crop of another' — meaning having intercourse with pregnant women among the captives. 'And that he should not have intercourse with a previously married woman from the captives until he has established her innocence [of pregnancy]' — meaning when he buys her. 'And that he should not sell any spoils of war until they are divided. 'And that he should not ride an animal from the spoils of the Muslims until, when he has made it lean, he returns it to them. 'And that he should not wear a garment from the spoils of the Muslims until, when he has worn it out, he returns it to them.'"