Musannaf Ibn Abi Shayba 28:1072

Isma'il ibn 'Ayyash narrated to us, from 'Abd al-Rahman ibn Ziyad ibn An'am, from Khalid ibn Abi 'Imran, who said: I heard al-Qasim and Salim saying: Whatever you cut from the trees of the enemy's land and fashioned into a peg, a club, a sledgehammer, a plank, a bowl, or a door, then there is no harm in it. And whatever you find of that already fashioned, then return it to the spoils of war.