[PAULUS libro quinto quaestionum. ] §2.14.43.prIn emptionibus scimus, quid praestare debitor debeat quidque ex contrario emptor: quod si in contrahendo aliquid exceptum fuerit, id seruari debebit.
[PAULUS, Questions, book 5] In sales we know what the debtor ought to perform and, on the contrary, what the buyer ought to perform; but if in contracting anything has been excepted, it must be observed.