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.”