Amr bin Shu'ayb narrates from his father, and he from his grandfather (Sayyiduna Abdullah bin Amr, may Allah be pleased with them both), that "the Messenger of Allah (peace and blessings be upon him) forbade a loan combined with a sale, two conditions in one sale, selling something that you do not have, and taking profit on something for whose loss one does not bear responsibility."
Hadith Referenceالسنن الكبرى للبيهقي / كتاب البيوع / 10828