Question: If reconciliation and mutual satisfaction have taken place between two disputants concerning a matter, and each of them has been content with what they reconciled upon, and each has fully waived every right and claim, then after that one of the two disputants finds a document indicating that he has more than what he accepted in the reconciliation – does he have the right to demand from his opponent, arguing that he only found the document after the reconciliation?
The answer, by Allah’s enabling, is that what appears to me is that the disputant has no right to demand anything from his opponent after the reconciliation and mutual satisfaction between them concerning a matter.
The proof of that is that the satisfaction of the two disputants with the reconciliation and their entering into it is in fact that each of them has been pleased with what has come to him by that reconciliation, and has yielded to his opponent whatever is beyond that.
Once the reconciliation has taken place on that basis, and mutual satisfaction with it has been completed in the presence of upright witnesses, then it is a valid reconciliation. A valid reconciliation is not undone except by a new reconciliation to undo it.
– And every reconciliation that takes place among the Muslims is valid and permissible, except a reconciliation that makes lawful what is unlawful or makes unlawful what is lawful; such a reconciliation is not valid. In this meaning the narration from the Prophet (May Allah bless him and his family and grant them peace) is authentic.
– There is no way to annul what has been correctly concluded of reconciliation; otherwise no reconciliation would ever be valid or stable, since it would always be possible for one of the two reconciled parties to claim that after the reconciliation something appeared to him indicating that he deserves more than that upon which the reconciliation was concluded.
Furthermore, reconciliation is stronger than a judicial ruling,
– because it is built upon the satisfaction of the two disputants with that upon which the reconciliation took place and their acceptance of it;
– and because Allah, Exalted, says: “And reconciliation is best” [al-Nisāʾ:128].
– And because reconciliation grants each of the two disputants ownership, both outwardly and inwardly, of that which has come to him by it, since it is built upon mutual satisfaction; whereas a judicial ruling only establishes ownership for the disputants outwardly.
– And if a correct judicial ruling is not, in general, annulled, then reconciliation is all the more not annulled.
– And Allah, Exalted, has said: “O you who have believed, fulfil (all) contracts.” [al-Māʾidah:1]
If it is said: When, after a judicial ruling, a decisive proof contrary to it becomes clear, that ruling is annulled. So likewise, if after a reconciliation a decisive proof contrary to what the reconciliation was concluded upon appears, [it should be annulled].
We say: The judicial ruling is only annulled when it contradicts a decisive proof because it becomes clear that it was invalid from the outset. As for reconciliation, the appearance of a decisive proof contrary to it does not invalidate it, because it is built upon the satisfaction of the two disputants, as we have already mentioned – and satisfaction is the strongest, or among the strongest, routes for transferring ownership.
Source: Min Thimār al-ʿIlm wa al-Ḥikmah vol.2