Sahih Muslim Book 10, Hadith Number 3645.

Chapter : It is invalid to sell the commodity before taking possession of it.

Ibn Umar (Allah be pleased with them) reported: We used to buy food-grains during the lifetime of Allah’s Messenger (may peace be upon him). He (the Holy Prophet) would then send to us one who commanded us to take them (the food-grains) to a place other than the one where we had bought them before we sold it.