with disparity, it is forbidden, just like selling one measure for two measures; this is because the grinding has separated its parts, so it results in a volume in its measuring container different from what results in the measuring container of wheat. Even if the disparity is not verified, equality is unknown, and ignorance of equality is like knowledge of disparity in matters where equality is a condition. For this reason, it is not permissible to sell some of it for some of it by guesswork. Their equality in weight does not necessarily imply equality in volume, and wheat and flour are measurable items because the original principle is measurement, and nothing has been found to shift it from that. Furthermore, flour resembles measurable items, so it is measured, like wheat. Even if it were weighed, equality would not be verified between a measurable and a weighable item, because the measurable cannot be estimated by weight, just as the weighable cannot be estimated by measurement.

Section: As for selling some of its derivatives for others, it is permissible to sell each one of flour and sawiq for its own type equally. This is the opinion of Abu Hanifa. The well-known position of al-Shafi'i is the prohibition of that, because he considers their equality in the state of perfection, which is the state of being wheat, and that state has been lost, since one of the two flours might be from heavy wheat and the other from light wheat (11), so they would be equal as flour but not equal as wheat. Our position is that they were equal at the time of the contract in a manner where neither one is uniquely deficient, so it is permissible, like selling dates for dates. When this is established, some of it is sold for some of it only by measurement, because wheat is a measurable item, and there is nothing in flour and sawiq that shifts them from that. It is stipulated that they be equal in fineness. Abu Bakr and others of our associates mentioned this, and it is the school of Abu Hanifa, because if they differ in fineness, they differ in the latter state, so it becomes like selling wheat for flour. Al-Qadi mentioned that flour is sold for flour by weight, but there is no basis for this, and he acknowledged regarding sawiq that it is sold by measurement, and flour is like it. As for selling flour for sawiq, the correct opinion is that it is not permissible, which is the school of al-Shafi'i. It is narrated from Ahmad that it is permissible, because each of them is parts of wheat with nothing else accompanying it, so it resembles flour for flour and sawiq for sawiq. Our position is that fire has affected one of them, so it is not permissible to sell some of it for some of it, like roasted grain