Musannaf Ibn Abi Shayba 28:495

Isma'il ibn 'Ayyash narrated to us, from 'Abd al-Rahman ibn Ziyad, from Khalid ibn Abi 'Imran, who said: I said to al-Qasim ibn Muhammad and Salim ibn 'Abd Allah: "A man among us is in the land of the enemy, and he hunts fish and sells them, and dirhams are gathered for him." They said: "There is no harm in that."