In the stated classical rule, a later market practice of pricing wheat per kilogram does not, by itself, erase the measure established in the text for the ribawi equality test.
Distinguish two questions: may a commodity be sold commercially in a modern known unit, and which quantity standard establishes equality when the same ribawi genus is directly bartered? The answers need not collapse into one undifferentiated rule.
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Riba: Operative Causes, Unequal Exchange and Deferral
In the stated classical rule, a later market practice of pricing wheat per kilogram does not, by itself, erase the measure established in the text for the ribawi equality test.
Distinguish two questions: may a commodity be sold commercially in a modern known unit, and which quantity standard establishes equality when the same ribawi genus is directly bartered? The answers need not collapse into one undifferentiated rule.