He replied:

A sale based on disclosure of the purchase price is permissible, whether at a profit, at a loss, at cost, or by selling a share at its proportionate cost. However, the seller and buyer must have the same knowledge of the price. If the seller purchased the item on deferred payment, the buyer must be informed of that. If he merely states a price without explaining that he purchased it on deferred payment, he is acting unjustly and wrongfully.

It is reported in the two Sahīh collections, from Hakīm ibn Hizām, that the Prophet, may Allah bless him and grant him peace, said:

“The buyer and seller retain the option to cancel the sale until they part. If they are truthful and make matters clear, their transaction will be blessed; but if they lie and conceal information, the blessing of their transaction will be erased.”

He—may Allah have mercy on him—was asked:

A merchant in a shop bought a piece of cloth for eleven and a quarter. Afterwards, a man came to him, and the merchant told him that he had purchased it for eleven and a quarter, then sold it to him at a profit of one-half. The buyer took it, and they parted company. An hour later, the buyer returned and sought to force the merchant to take it back. The merchant refused and did not disclose the profit, but the buyer would not relent, and they disputed the profit.

The buyer said, “Take a quarter and an eighth from me.” The merchant said to the buyer, “Sell it to me for eleven and a half.” He replied with the word “Yes.” May he disclose this additional quarter to the original buyer? Is doing so permissible for him in any way?

He replied:

The owner of the merchandise may not state that he purchased it for that amount without