Musnad Ahmad 448:1

Yahya ibn Zakariya ibn Abi Za'idah narrated to us, he said: Muhammad ibn Ishaq narrated to me, from Yazid ibn Abi Habib, from Abu Marzuq—the freed slave of Tujib, and Tujib is a sub-tribe of Kindah—from Ruwayfi' ibn Thabit al-Ansari, who said: I was with the Prophet, peace and blessings of Allah be upon him, when he conquered Hunayn. He stood among us as a preacher and said: "It is not lawful for a man who believes in Allah and the Last Day to water the crop of another with his water. And he should not purchase spoils of war until they are divided. And he should not wear a garment from the spoils of the Muslims until, when he has worn it out, he returns it to them. And he should not ride a beast from the spoils of the Muslims until, when he has made it lean, he returns it to them."