Abdullah bin Muhammad bin Sayfi narrated from Hakim bin Hizam (may Allah be pleased with him) that the Prophet (peace and blessings be upon him) said: "Have I not been informed, or have I not been told, or has it not reached me" (or he said something to that effect, as Allah willed) "that you sell foodstuffs?" I said: Yes. He (peace and blessings be upon him) said: "Then when you buy foodstuffs, do not sell them until you have received them in full."
Hadith Referenceالمعجم الكبير للطبراني / باب الحاء / 3083