Al-Shafi'i said: Reconciliation over an unknown [amount] is not valid, because it is a branch of a sale, and a sale is not valid over an unknown [amount]. Our evidence is what has been narrated from the Prophet, peace and blessings of Allah be upon him, that he said regarding two men who disputed over forgotten inheritances: "Cast lots, be fair to one another, and let each of you absolve the other." This is reconciliation over an unknown [amount]. Furthermore, it is a waiver of a right, so it is valid regarding an unknown [amount], just like manumission and divorce. Also, if reconciliation is valid with knowledge and the possibility of delivering the exact right, then its validity with ignorance is even more appropriate. This is because if it is known, they both have a way to be released and for one to be absolved of the other without it [reconciliation], whereas with ignorance, that is not possible; thus, if reconciliation were not permitted, it would lead to the loss of wealth, assuming there is wealth between them, the share of which neither of them knows. We do not concede that it is a sale, nor a branch of a sale; it is merely a discharge of obligation (ibra'). Even if we were to concede that it is a sale, it is valid regarding the unknown in cases of necessity, evidenced by the sale of foundations of walls, the lining of wells, and items whose edible parts are hidden inside. If a man destroyed a heap of food, the amount of which he does not know, and the owner of the food said to the one who destroyed it: "I have sold you the food that is in your liability [for these dirhams], or for this garment," it is valid. Once this is established, if the compensation in the reconciliation is of a type that does not need to be handed over and there is no way to know its amount—such as those disputing over forgotten inheritances, past rights, or a specific item of wealth of which neither knows the extent of his right—the reconciliation is valid despite the ignorance on both sides, due to the report and the rationale we mentioned. If, however, it is of a type that requires handing over, it is not permitted with ignorance, and it must be known, because its delivery is obligatory, and ignorance prevents delivery and leads to dispute, thus defeating the purpose of reconciliation.

Section: As for that which they are able to know, such as an existing estate, or that which the party who owes it knows while its owner is ignorant of it, reconciliation over it is not valid while there is ignorance. Ahmad said: If a woman is reconciled over her eighth share...