His statement, “he sells it at its marked price,” means at a price that is unknown at the time of the contract.

His statement, “or for one thousand dirhams, in gold and silver”: this issue has two forms:

The first is for him to say, “I sell it to you for one thousand, in gold and silver.”

The second is for him to say, “I sell it to you for one thousand dirhams, in gold and silver.”

According to the madhhab, the sale is invalid in both cases. It has also been said that it is valid in both cases, with the amount understood as being divided equally: five hundred dirhams and five hundred dinars. However, if he says, “For one thousand dirhams, in gold and silver,” we do not know how much he will give: he may give the greater part in gold and the remainder in silver, or vice versa; thus, we do not know.

But one might argue: if the exchange rate between dirhams and dinars is fixed, such that every twelve dirhams equal one dinar, then when he says, “I sell it to you for one thousand dirhams, in gold and silver,” the amount is known, and the sale is valid whether payment is made in dinars or dirhams.

However, he may have a legitimate interest in having most of the price paid in dinars, or most of it paid in dirhams. Therefore, the author’s view that it is invalid is correct. Even if it is assumed that the relative value of dirhams and dinars does not change, he may still have an interest in specifying which of them is to be paid.

In summary: if he says, “I sell it to you for one thousand, in gold and silver,” the sale is valid, and the amount is understood as being divided equally. But if he says, “For one thousand dirhams, in gold and silver,” it is invalid, because he may make the greater portion gold and the lesser portion silver, or vice versa. Likewise, if he says, “For one hundred dinars, in gold and silver,” it is invalid due to uncertainty.