Seventh: the option arising from disagreement between the two parties to a sale. If they disagree over the amount of the price, they must both swear an oath. The seller swears first: “I did not sell it for such-and-such; rather, I sold it for such-and-such.” Then the buyer swears: “I did not buy it for such-and-such; rather, I bought it for such-and-such.”
His statement, “Seventh: the option arising from disagreement between the two parties to a sale”: Disagreement between contracting parties has existed since ancient times. They may disagree regarding the type, amount, description, or specific item, or regarding a term or a condition; and such disagreements are countless.
The scholars, may Allah have mercy on them, have mentioned principles resembling general rules in this chapter, since it is impossible to encompass every individual case. Not every disagreement gives rise to an option; rather, it is the type of disagreement for which the sunnah indicates that an option is established. This is why al-Rawd says, “in general” (1). When jurists say “in general,” they mean most cases; but when they say “as a whole,” they mean all cases. This is their established terminology. The difference is that “in” indicates inclusion within a category, whereas the prefix “by” conveys comprehensiveness.
His statement, “If they disagree over the amount of the price”: For example, the seller says, “I sold it for ten,” while the buyer says, “I bought it for eight,” and no evidence is available. If evidence is found supporting the statement of either one of them, then the matter is clear: judgment is made in accordance with what the evidence establishes.
Can circumstantial indication be of use here? That is, suppose it is said that what the buyer claims is closer to the market price than what the seller claims.
The answer is that this requires further detail. If what either of them claims is so far-fetched as to be impossible, it is not accepted, given any consideration, or heard. But if it is plausible, then the ruling is as the author states and will mention, if Allah wills.