What is the ruling on combining a lawful sale item with an unlawful sale item in a single transaction for a single price?
Chapter on Selling the Musarrah (Animal with milk retained in udder)
Al-Mughni
Book of Sales
Primary text
If a sale combines an item whose measure or quality is known (ma'lum) with an item whose measure or quality is unknown (majhul) for a single price, the sale is void in all circumstances. The grounds for invalidity are that the unknown item cannot be legitimately sold due to its ambiguity, and the known item has an indeterminate price. Since the price cannot be apportioned, determining the value of the unknown item becomes impossible, thus invalidating the entire transaction.