[PAULUS libro tertio quaestionum. ] §12.5.8.prSi ob turpem causam promiseris Titio, quamuis, si petat, exceptione doli mali uel in factum summouere eum possis, tamen si solueris, non posse te repetere, quoniam sublata proxima causa stipulationis, quae propter exceptionem inanis esset, pristina causa, id est turpitudo, superesset: porro autem si et dantis et accipientis turpis causa sit, possessorem potiorem esse et ideo repetitionem cessare, tametsi ex stipulatione solutum est.
[PAULUS, Third Book of Questions.] If you have promised Titius for an immoral cause, although, if he should sue, you could defeat him by the plea of fraud or a plea on the facts, nevertheless, if you have paid, it is held that you cannot recover; for when the immediate cause of the stipulation, which would have been ineffectual on account of the plea, is removed, the original cause, that is, the immorality, remains. Furthermore, if the cause is immoral on the part of both the giver and the receiver, the possessor has the better position, and therefore recovery is barred, even if payment was made on the basis of a stipulation.