عَنْ جَابِرٍ قَالَ: إِنَّ رَسُولَ اللَّهِ صَلَّى اللَّهُ عَلَيْهِ وَسَلَّمَ نَهَى عَنِ الثُّنْيَا إِلَّا أنْ يُعلمَ. رَوَاهُ التِّرْمِذِيّ

Hakim b. Hizam said God's Messenger forbade him to sell anything which was not in his possession.Tirmidhi transmitted it.In a version by Abu Dawud and Nasa’i, he had said, “Messenger of God, a man comes to me and wants me to sell him something, but I do not have it and so I buy it for him from the market.” He replied, “Do not sell what you do not possess.”