Yusuf bin Mahak narrated from Hakim bin Hizam (may Allah be pleased with him), who said: I said: O Messenger of Allah! A man comes to me and asks me for something that I do not have; should I obtain it from the market and sell it to him? He (peace and blessings be upon him) said: "Do not sell what you do not have."
Hadith Referenceالمعجم الكبير للطبراني / باب الحاء / 3086