De transactionibus axiomata

XCIII Note: The text jumps from XCIII to XCV, likely a typo in the original numbering..
For either the cause is not expressed in the settlement, nor is it held as expressed, and it is certain that nothing can be attempted against the settlement in this case.

XCV.
Or a cause has been added, or at least verisimilarly considered by both parties settling, so that it is held as added; then, if it is honest, and that cause has not followed, the settlement can only be retracted if the party who stood in the way of the promises being fulfilled remained in default until the contestation of the suit, for it is more probable that the default committed can be purged in this case up to that point.

XCVI.
But if the cause is shameful and contrary to good morals, the settlement will remain in its own right and state, even if that cause does not follow.

XCVII.
Similarly, a suit that has been decided is not reopened on account of an eviction of a thing that was handed over for the sake of the settlement, provided that another action is available by which the adversary may be urged to comply with the agreements.

XCVIII.
Much less, however, will it be possible to rescind a settlement because a thing left to the defendant on account of the settlement has been evicted from him.

XCIX.
Furthermore, if no intermediate thing was involved, a settlement interposed in good faith is valid, provided that evident calumny by either of the settling parties is not discovered.

C.
Consequent to this is that he who has given or promised something to an adversary for the sake of a settlement cannot seek it back as an undue payment.