The question then arises: who is responsible for reaping the crop and threshing it?
The scholars of Kūfah say: the duty lies with the seller until he separates the grain and hands it over as clean kernels to the buyer, whereas others hold that the obligation is on the buyer.
Under the same heading falls the authenticated report that “the Messenger of God—may God bless him and grant him peace—forbade two sales within a single sale.” It is transmitted by Ibn ʿUmar, Ibn Masʿūd, and Abū Hurayrah. Abū ʿUmar states that all of these narrations come through upright transmitters. The jurists therefore agree on affirming the general import of the ḥadīth, but they differ over the particulars—that is, the concrete forms to which the prohibition applies and those to which it does not. They likewise concur regarding certain cases.
These cases can be envisaged in several patterns, the most important of which are three:
- Two distinct goods for two separate prices;
- One good for two different prices;
- Two goods for a single price, both sales having become binding.
I. Two goods for two prices.
This appears in two ways:
(a) A man says, “I sell you this merchandise for such-and-such provided that you sell me that house for such-and-such”;
(b) Or he says, “I sell you this merchandise for one dinar, or that other merchandise for two dinars.”
II. One good for two prices.
This, too, has two ways:
(a) One of the two prices is for cash and the other on credit, as when he says, “I sell you this garment for such-and-such in cash, on condition that I buy it back from you at a stated date for such-and-such.”
III. Two goods for one price.
An example is his saying, “I sell you one of these two items for such-and-such.”
With respect to the first configuration—“I sell you this house for such-and-such on condition that you sell me this slave for such-and-such”—al-Shāfiʿī ruled it impermissible, because in both sales the price remains unknown: if each item were sold separately, the parties would not necessarily agree on the same price they set when combining the two transactions in a single contract. Al-Shāfiʿī’s underlying reason for rejecting “two sales in one sale” is precisely the uncertainty affecting either the price or the object sold.
As for the second configuration—“I sell you this commodity for one dinar, or that other one for two dinars,” with the sale becoming binding in one of the two—this, according to all the jurists, is invalid, whether the stated currency is the same or different. ʿAbd al-ʿAzīz ibn Abī Salamah dissented, however, and declared it permissible in both cases. The common rationale for prohibiting it is the ambiguity involved; Mālik adds the principle of blocking the means, for the seller may privately choose one of the two garments and thus end up exchanging a garment and a dinar for another garment and a dinar—something inadmissible according to Mālik’s foundational rules.
As for the third configuration—namely, his saying, “I sell you this garment for such-and-such in cash, or for such-and-such on credit,” this is valid if