Thus, the ruling for their derivatives follows the same principle. Our position is that weight is more concise, so it must be considered for items that are neither measured nor weighed, such as items that cannot be measured. Measurement was only considered for the items explicitly mentioned because they are customarily estimated by it, and this [case] is different.

709 - Issue: He said: "And all dates are one genus (1), even if their types differ."

Genus is that which encompasses things differing in their types. Type is that which encompasses things differing in their individuals. A type may be a genus in relation to what is beneath it, and a type in relation to what is above it. The intent here is the most specific genus and the most specific type. Every two types that gather under a specific name are a genus, such as the types of dates and the types of wheat. Thus, all dates are one genus because the specific name gathers them, which is "date," even if its types are numerous, such as Al-Barnī (2), Al-Ma‘qalī (3), Al-Ibrāhīmī, Al-Khāstawī (4), and others. Every two things that agree in genus have the legal ruling of the prohibition of usurious excess (tafadul) established between them, even if the types differ, due to the saying of the Prophet, peace and blessings be upon him: "Date for date, like for like, [and wheat for wheat, like for like] (5)." The hadith in its entirety (6). He considered equality in the genus of date for date, and wheat for wheat, then said: "But if these classes differ, then sell as you wish" (7). In another wording: ["But if the two genera differ, then sell as you wish. And in another wording"] (8): "Except for that whose colors differ."