What is the ruling on saying: 'I sold you this heap, every qafiz for one dirham, on the condition that I add one qafiz from this other heap'?

Primary text

The sale is invalid because it leads to the ambiguity of the total price in detail, as it effectively becomes 'one qafiz plus an unknown amount for one dirham.' The ambiguity arises from the lack of knowledge regarding the total number of qafizes in the heap.