Narrated Tawus:Ibn `Abbas said, "Allah's Messenger (ﷺ) forbade the selling of foodstuff before its measuring and transferring into one's possession." I asked Ibn `Abbas, "How is that?" Ibn `Abbas replied, "It will be just like selling money for money, as the foodstuff has not been handed over to the first purchaser who is the present seller

English translation · Sahih al-Bukhari