Amr bin Shu'ayb narrates from his father, and he from his grandfather (may Allah be pleased with him), that the Messenger of Allah (peace and blessings be upon him) said: "A loan combined with a sale is not lawful, two conditions in one sale are not valid, taking profit on something for which one has not borne liability is not valid, and selling what is not with you is not permissible."
Hadith Referenceالسنن الكبرى للبيهقي / كتاب البيوع / 10419