by a mudy, and barley for barley is a mudy by a mudy, and salt for salt is a mudy by a mudy; so whoever gives more or receives more has practiced usury." Thus, he ordered equality in the weighed items mentioned regarding weight, just as he ordered equality (4) in measured items regarding measure. Anything other than gold and silver among weighed items is measured against them and analogized to them; and because it is a genus in which usury occurs, it is not permissible to sell some of it for others by estimation (juzaf), just like measured items. Furthermore, because it is a weighed item among the items of usury, it resembles gold and silver. Moreover, the reality of excess invalidates the sale, and we do not know of the absence of such [excess] except by weight; therefore, it became mandatory, just as it is in measured items and currencies. When this is established, it is not permissible to sell a measured item for a measured item by weight, nor a weighed item for a weighed item by measure; because equality in measure is a condition for measured items, and equality in weight is a condition for weighed items. Thus, whenever one sells a ritl of measured items for a ritl, the lighter item yields more than what the heavier item yields, so they differ in measure. Even if one does not know of the excess, one is still ignorant of the equality, so it is not valid, just as if one sold some of it for others by estimation. Likewise, if one sells a weighed item for a weighed item by measure, equality in weight is not realized, so it is not valid, as we have mentioned regarding measured items.

Section: If one sells some of it for others by estimation, or if it is estimation from one of the two parties, it is not permissible. Ibn al-Mundhir said: The scholars have reached a consensus that this is not permissible if they are of the same kind. This is due to what Muslim (5) narrated from Jabir, who said: The Messenger of God - may God bless him and grant him peace - prohibited the sale of a heap (subra) of dates, whose measure is unknown, for a specified measure of dates. In the statement of the Prophet - may God bless him and grant him peace -: "Gold for gold by weight for weight" (6) until the end of the hadith, there is evidence that it is not permissible to sell it except in that manner, and because equality is a condition, and ignorance of it invalidates the sale, just as the reality of disparity does.