Case: A man buys a soiled garment for ten dirhams, then gives it to a fuller—that is, a washer—who washes it for two dirhams. He has thus acquired it for twelve dirhams. If someone then comes to him and says, “I want you to sell it to me at cost,” and he replies, “Its cost is twelve dirhams,” this is not permissible, even though he has acquired it only for twelve dirhams. Rather, he must say, “I bought it for ten dirhams and had it washed for two dirhams.” All of this is in pursuit of truthfulness in transactions, for the Prophet ﷺ said concerning two parties to a sale: “If they are truthful and make matters clear, their sale will be blessed; but if they lie and conceal, the blessing of their sale will be erased.” (1)

Accordingly, everything that changes the situation in a sale at cost must be disclosed.

His statement, “And if he discloses the circumstances,” means even if he does so after the contract has become binding.

His statement, “then that is preferable”: In al-Rawd, he explained this by saying, “Because it is more conducive to truthfulness.” (2)

Case: Is he required to disclose the earnings of a slave and the separately accrued offspring or produce of an animal, deducting them from the price, or is he not required to do so?

The answer: He is not required to do so. Thus, if he buys a slave for ten thousand, and the slave remains with him for a month or two and earns two thousand during that period, then he sells him at cost and says, “His cost is ten thousand,” he does not add the two thousand to it, because this is separate increase, and it belongs to the buyer, since it arose while the slave was in his ownership.