What is the ruling on selling a Ribawi item mixed with a substantial, yet purposeful, non-Ribawi substance?

Primary text

If the admixture is substantial but serves the purpose of the intended item, such as water in date vinegar, raisins, or date molasses, then selling the item for its like is permissible. The mixture is treated like its natural moisture, thus it does not prevent selling it for an equivalent item, such as fresh dates for fresh dates. However, selling it for an item lacking the admixture is impermissible, such as selling grape vinegar for date vinegar, as this leads to unequal exchange (*tafāḍul*), resembling selling fresh dates for dried dates. The Shafi'i school prohibits all such sales except the sale of *shīraj* (a mixture of oil and sesame paste) for itself, because the water content is not apparent in *shīraj*.