Narrated Ibn `Abbas
The Prophet (ﷺ) forbade the selling of foodstuff before receiving it. I consider that all types of sellings should be done similarly.
Narrated Ibn `Umar
The Prophet (ﷺ) said, "The buyer of foodstuff should not sell it before it has been measured for him." Isma`il narrated instead, "He should not sell it before receiving it."