like the price. We know of no disagreement regarding the consideration of knowing the amount. It is obligatory to estimate it with a measure or weights known to the public. If he estimates it with a specific container (3) or a specific weight-stone that is not known, it is not valid, because it might perish, making it impossible to know the amount (4) of the commodity in the Salam contract, and this is an uncertainty (gharar) that the contract does not require. Ibn al-Mundhir said: All scholars we have memorized from are in consensus that a Salam contract for food is not valid with a qafiz whose calibration is unknown (5), nor for a garment with someone's [specific] measure; because if the standard were destroyed, or that person died, the Salam contract would be void; among them are al-Thawri, al-Shafi'i, Abu Hanifah and his companions, and Abu Thawr. If he specifies a man's measure or his scale, and they are known to the public, it is permissible; it is not restricted to them. If they are not known, it is not permissible.

Section: If he enters into a Salam contract for something that is measured, by weight, or for something that is weighed, by measure, al-Athram reported that he asked Ahmad about a Salam contract for dates by weight. He said: "No, only by measure." I said: "The people here do not know the measure." He replied: "Even if they do not know the measure." This implies that it is not permissible for what is measurable except by measure, and not for what is weighable except by weight. This is what was mentioned by the Qadi and Ibn Abi Musa (6). This is because it is an object of sale for which knowledge of its amount is a condition; therefore, it is not permitted using anything other than that which it is originally measured by, like selling moisture-containing goods for each other. Because he has estimated the subject of the Salam contract by something other than what it is originally measured by, it is not permitted, just as if he had entered a Salam contract for something measured by length, using weight. Al-Marwudhi reported from Ahmad that it is permissible to enter a Salam contract for milk if it is by measure or weight. This indicates the permissibility of a Salam contract for measurable goods by weight, and for weighable goods by measure, because milk is inevitably either measurable or weighable, and he has permitted the Salam contract for it by either of the two. This is the view of al-Shafi'i and Ibn al-Mundhir. Malik said: That is permissible if the people trade dates by weight. This is more correct, if Allah the Exalted wills, because the purpose is...