Exchange of One Kind of Food Items for another Kind

3. Ali ibn Ibrahim has narrated from his father from Ibn Abi ‘Umayr from Hammad ibn ‘Uthman from al-Halabiy who has said the following: “Abu ‘Abd Allah عليه السلام, has said, ‘It is not permissible to sell two Makhtum (a container) of barley for one Makhtum of wheat. These items cannot be exchanged except in equal quantities of each other and so also is the date.’ Abu ‘Abd Allah عليه السلام, was asked about the case of a man who buys wheat but cannot find with his party anything except barley, if he can take two for one. He (the Imam) said, ‘No, because the origin of the two is the same and Ali عليه السلام, would count barley for wheat.’”