An example of this is where one person sells a car to another, its market value being sixty thousand, and then they disagree about the price. The seller says, “I sold it for sixty thousand,” while the buyer says, “I bought it for ten thousand.” This could only be due to some particular reason, whereas the basic presumption is that no such reason exists. Thus, if someone were to offer for sale a car worth sixty thousand for ten thousand, it would be said, “He has stolen it,” or, “There is something wrong with it.” As we said previously regarding a defect: if only one of their statements is plausible, it is accepted without an oath.

His statement, “They both swear an oath,” means that each one swears an oath (1). This is conditional upon there being no evidence or circumstantial indication disproving either of their claims.

If someone were to ask: How can we require both of them to swear an oath when the Prophet, peace and blessings be upon him, said: “Proof is upon the claimant, and the oath is upon the one who denies” (2)?

We answer: In reality, each of them is both a claimant and a denier, so each of them is required to swear an oath. The seller claims that the price was one hundred and denies that it was eighty, while the buyer claims that it was eighty and denies that it was one hundred. This is why we require each of them to swear an oath; thus, they both swear.

His statement, “The seller swears first: ‘I did not sell it for such-and-such; rather, I sold it for such-and-such,’” is because ownership passed from him, so his position is stronger. The basic presumption is that property does not leave its owner’s possession. Moreover, the seller seeks to establish something, whereas the buyer seeks to negate it; and negation only comes after affirmation. Therefore, the seller swears first, saying, “By Allah, I did not sell it for such-and-such; rather, I sold it for such-and-such.” In the example at hand,