The reasoning of those who hold that, once the excess has been deducted, the sale remains binding is this: the buyer granted the seller a profit only on the price for which the latter had actually purchased the commodity, nothing beyond that. When it emerges that the seller’s statement was false, he must revert to what has come to light—exactly as if a man had contracted for a known measure of grain but found the measure deficient: he would be obliged to make up the shortfall.

Those who grant an unqualified option to rescind base their view on an analogy between falsehood in this matter and a defect, meaning that just as a defect gives rise to an option, so does lying.

If the goods have perished, al-Shāfiʿī rules that the seller must deduct the entire amount that was added to the price, including whatever profit was due. Mālik says: if their value on the day of possession—or, according to another report from him, on the day of sale—was equal to or less than the sum the purchaser had paid, the buyer has no claim against the seller. If their value was lower, the seller may choose between refunding the buyer that value, refunding him the price he paid, or letting the sale stand at the verified price.

When a man sells his goods by murābaḥah, then produces testimony that their purchase price was higher than he had stated—claiming a mistake—while the goods are still in existence, al-Shāfiʿī says such testimony is not accepted, for the seller has already contradicted it. Mālik, by contrast, accepts the testimony and compels the purchaser to pay the higher price—though this is improbable, for it would constitute a new sale. Mālik further states that, should the goods have perished, the purchaser may either pay their value on the day he took possession of them or keep the transaction at the price that stands validated. These are the most famous issues discussed in this chapter.

In the Mālikī school, grasping the rulings of this type of sale depends on understanding three questions and the combinations that arise from them: the ruling on lying, the ruling on cheating (ghish), and the ruling on the presence of a defect.

1. The ruling on lying has already been explained.
2. The ruling on rescission for a defect is the same as in ordinary sales.
3. As for cheating, Ibn al-Qāsim holds that the seller has an unrestricted option to rescind; the buyer cannot compel him to complete the sale even if the seller deducts the amount involved in the deception—unlike the case of lying.

Ashhab, however, divides cheating into two kinds: one that affects the price and one that does not. The latter carries no legal consequence, whereas the former is treated the same as lying.

There are four compounded scenarios: (i) lying and cheating; (ii) lying and concealment (tadlīs); (iii) cheating and concealment accompanied by a defect; and (iv) lying, cheating, and concealment accompanied by a defect. The guiding principle in Ibn al-Qāsim’s school is to apply whichever ruling still remains if one of them has lapsed, or the ruling that is weightier where none has lapsed—either by giving the parties a choice when that is possible, or by combining rulings when combination is possible. The full elaboration of this belongs in the books of substantive jurisprudence—that is, in the works of Ibn al-Qāsim and others.