Sayyiduna Fadalah bin Ubayd (may Allah be pleased with him) said: The greatest effort these people are making is to make me abandon my religion, but that will not happen until I meet Muhammad (peace and blessings be upon him) and his Companions: "Whoever sells food or fodder from what was taken (as spoils) in the land of the Romans for gold or silver, then the one-fifth (khums) of Allah and the shares of the Muslims become due on it."
Hadith Referenceالمعجم الكبير للطبراني / باب الفاء / 15857