It is narrated from Sayyiduna Attab bin Asid (may Allah be pleased with him) that when the Prophet (peace and blessings be upon him) appointed him governor of Makkah, he said to him: "Will you convey from me to your people what I command you? Tell them: No one should combine a sale and a salam (advance-payment sale), no one should make a sale involving deception (gharar), and no one should sell what he does not have."
Hadith Referenceالمعجم الكبير للطبراني / باب العين / 14497