Musannaf Ibn Abi Shayba 28:815

Waki’ narrated to us, he said: Isra’il narrated to us, from Jabir, from ‘Amir, who said: There is no harm in food and fodder found in the land of the enemy, that they eat from it and feed their beasts from it. As for what is sold of it, it is [to be divided] among the Muslims.