First: if he says, “No deception,” he has the option of rescission in any case in which he is overcharged, whether the disparity exceeds customary limits or not. This is because lā is a particle that negates the entire category, and khilābah is an indefinite noun occurring in the context of this categorical negation, thereby conveying generality—that is, no deception, whether slight or substantial.
Second: it settles the dispute between the two parties. If he does not stipulate that there is to be no deception, the seller may say, “I did not overcharge you.” But as soon as he says, “No deception,” the seller will refrain from deception from the outset, for if this is stipulated, he will know that should he overcharge him, the buyer will return the goods to him. This, then, is the benefit of the Prophet’s ﷺ guidance to this man to stipulate that there be no unfair overcharging. Accordingly, the preponderant view is that the option due to unfair disparity in price is established, whether or not it was stipulated.
His statement, “exceeds customary limits,” refers us back to customary practice. Whatever people regard as unfair disparity is such, and whatever they do not regard as unfair disparity is not. Some scholars have set its threshold at one-third, others at one-fourth, and others at one-fifth.
However, the author’s view—that the matter should be referred to customary practice—is more correct. Those whose judgment determines customary practice are the experts. Thus, if they say, “This is unfair disparity because it exceeds customary limits,” we say that he has the option of rescission.
Question: Is the option due to unfair disparity restricted to particular cases, or does he acquire the option whenever such disparity occurs?
Answer: There is a difference of opinion on this issue. According to the madhhab, the option due to unfair disparity is confined to three situations:
The first situation is intercepting incoming traders: that is, for someone to leave the town in order to meet those bringing goods into it and buy from them. It is well known that the one who intercepts them