Do wheat and barley constitute a single commodity category (jins)?
Chapter on Riba (Usury) and Exchange (Sarf)
Al-Mughni
Book of Sales
Primary text
Wheat and barley are two distinct commodity categories. They are distinct because they do not share a specific collective name, similar to dates and wheat. Additionally, since they are both specifically named items within the six regulated categories (of staple foods), they must be considered as two separate categories, like all others in those classifications.
Supporting text
The counter-argument posits that they are a single category because one can contaminate the other (yughashshu bi-l-akhar), thus treating them as two types of the same category, drawing an analogy from the discussion concerning the two types of vinegar.