Muhammad bin Zaid (may Allah have mercy on him) says that I asked Hazrat Ibn Umar (may Allah be pleased with them) that sometimes a person enters into a salam sale with someone for one thousand dirhams, and says: If you give me wheat, the deal will be for such and such amount, and if you give barley, then for such and such amount. He (may Allah be pleased with him) replied: For each type (kind), state a separate price; if he gives it to me at that price, then fine, otherwise take back your principal amount from him.