“Keep it”—that is, keep the defective item sold—“with an arsh (a proportionate price abatement), which is the proportion between its value when sound and when defective.” The author explained arsh by saying, “the proportion,” meaning the proportion between its value when sound and when defective. He said “value,” not “price.” The difference between value and price is that value is what it is worth in the market generally, whereas the price is what the contract was concluded for. Thus, if you buy something worth eight for six, its value is eight and its price is six.
For this reason, be attentive when drafting contracts: do not say, “He sold it to him at a value of such-and-such”; rather, say, “at a price of such-and-such.” How many writers make this mistake! Or one may say, “He sold it at a price of such-and-such, and the value has been received,” whereas instead of saying “the value,” one should say, “the price has been received.”
This is why he said, “the proportion between its value when sound and when defective.” The item is appraised as sound and then appraised as defective. The ratio between its sound value and defective value is then taken as the arsh, and the corresponding proportion is deducted from the price. The appraisal is to be made at the time of the contract, not at the time the defect becomes known, because the value may differ between the time of the contract and the time the defect is discovered.
For example, someone sells a car worth one hundred thousand for fifty thousand, and then a defect is found in it. We ask the experts to assess the defect, and they say: “As defective, it is worth eighty, and as sound, it is worth one hundred.” The arsh is now one-fifth. Since the price was fifty thousand, ten thousand is deducted. If we were to say that the difference between the two values should simply be deducted, the deduction would be twenty thousand, leaving the price at thirty thousand. This is incorrect. If he sold it for two hundred thousand and a defect then became apparent, the car would be appraised, and it would be said that