Sahih Muslim
The Book of Transactions (Kitab Al-Buyu)
Book Number: 010 / Hadith Number: 3645
Ibn Umar (Allah be pleased with them) reported: We used to buy foodgrains 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 foodgrains) to a place other than the one where we had bought them before we sold it.