"The Messenger of Allah forbade lending on the condition of a sale, selling what you do not have, and profiting on what you do not possess. (Using translation from Nasāʾī 4631)
نَهَى رَسُولُ اللهِ ﷺ عَنْ سَلَفٍ وَبَيْعٍ وَعَنْ بَيْعَتَيْنِ فِي بَيْعَةٍ وَعَنْ بَيْعِ مَا لَيْسَ عِنْدَكَ وَعَنْ رِبْحِ مَا لَمْ يُضْمَنْ