Musannaf Ibn Abi Shayba 13:2361

Abu Bakr narrated to us, he said: Abu al-Ahwas narrated to us, from Simak, from Tha'labah ibn al-Hakam, who said: We obtained sheep belonging to the enemy and we plundered them, then we set up our cooking pots. The Prophet, peace and blessings of Allah be upon him, ordered the pots to be overturned. And he said: "Plunder is not lawful."