al-Athram, because the apparent implication is that they only contract using it. If there are multiple currencies in the land, one reverts to the most common (awsat). This was stated as a text (nass) in the narration of a group. It is possible he meant when it is the dominant one and the most frequently used in dealings, because the apparent implication is that the transaction occurs using it, so it is as if there were only one currency in the land. It is also possible that he referred both of them to it alongside equality, because it involves a median between them and an equalization of their rights, and in turning to another there is a bias toward one of them, so the median is more appropriate. Upon the claimant of that rests the oath, because what his opponent said is plausible, so the oath becomes mandatory to negate that possibility, just as its obligation upon a denier. If there are only two equal currencies in the land, it is appropriate that they mutually swear, because they differed regarding the price in a manner where the statement of neither is given precedence, so they mutually swear, just as if they had differed regarding its amount.

Section: If they differ regarding a deferment (ajal), a pledge (rahn), or the amount of either, or a condition of an option (khiyar), or a guarantor, or any other valid conditions, there are two narrations concerning it. One of them is that they shall mutually swear. This is the opinion of al-Shafi'i, because they differed regarding the attribute of the contract, so it became necessary for them to mutually swear, by analogy to the disagreement regarding the price. The second is that the statement is the statement of the one who denies that, along with his oath. This is the opinion of Abu Hanifa, because the default principle is its absence, so the statement is the statement of the one who denies it, like the origin of the contract, for he is a denier, and the statement is the statement of the denier.

Section: If they differ regarding that which invalidates the contract or a corrupt condition, and one says: 'I sold you for wine, or for an unknown option,' and the other says: 'Rather, you sold me for a known currency, or for an option of three days,' the statement is the statement of the one who claims the validity, along with his oath; because the appearance of the Muslim's engagement in valid transactions is more frequent than his engagement in corrupt ones. If he says: 'I sold you under duress,' and the other denies it, the statement is the statement of the buyer, because the default principle is the absence of duress and the validity of the sale. If he says: 'I sold you while I was a child,' the statement is the statement of the buyer. This was stated as a text (nass) by him, and it is the opinion of al-Thawri and Ishaq, because they agreed upon the contract.