[IDEM libro tertio regularum. ] §12.6.40.prQui exceptionem perpetuam habet, solutum per errorem repetere potest: sed hoc non est perpetuum.
[IDEM libro tertio regularum.] A person who has a perpetual exception can recover what has been paid by mistake; but this is not universally true.
nam si quidem eius causa exceptio datur cum quo agitur, solutum repetere potest, ut accidit in senatus consulto de intercessionibus: ubi uero in odium eius cui debetur exceptio datur, perperam solutum non repetitur, ueluti si filius familias contra Macedonianum mutuam pecuniam acceperit et pater familias factus soluerit, non repetit.
For if indeed the exception is granted for the sake of the person who is sued, he can recover what was paid, as happens under the senatusconsultum on intercessions; but where the exception is granted out of hatred for the person to whom the debt is owed, what was paid by mistake is not recovered, as for example, if a filius familias has accepted a loan of money contrary to the Senatusconsultum Macedonianum and, having become a pater familias, has paid it, he does not recover it.
§12.6.40.1Si pars domus, quae in diem per fideicommissum relicta est, arserit ante diem fideicommissi cedentem et eam heres sua impensa refecerit, deducendam esse impensam ex fideicommisso constat et, si sine deductione domum tradiderit, posse incerti condici, quasi plus debito dederit.
If a part of a house, which was left by way of fideicommissum subject to a future day, should burn down before the day of the vesting of the fideicommissum, and the heir should rebuild it at his own expense, it is well established that the expense is to be deducted from the fideicommissum; and if he should deliver the house without deduction, a condictio incerti can be brought, as if he had given more than was due.
§12.6.40.2Si pactus fuerit patronus cum liberto, ne operae ab eo petantur, quidquid postea solutum fuerit a liberto, repeti potest.
If a patron has made an agreement with his freedman that services should not be demanded from him, whatever is subsequently paid by the freedman can be recovered.