Musannaf Ibn Abi Shayba 28:803

Isma'il ibn 'Ayyash narrated to us, from Usayd ibn 'Abd al-Rahman, from Khalid ibn al-Durayk, from 'Abd Allah ibn Muhayriz, who said: Fudalah ibn 'Ubayd, the chamberlain of the Messenger of Allah (may Allah bless him and grant him peace), was asked about selling food and fodder in the land of the Romans. Fudalah said: "Indeed, some people want to cause me to slip from my religion. By Allah, I hope that will not happen until I meet Muhammad (may Allah bless him and grant him peace). Whoever sells food for gold or silver, the fifth [share] of Allah and the shares of the Muslims become due upon it."