7 Under certain circumstances money which is not owed, and which is paid by mistake, is not recoverable; the rule of the older lawyers on this point being that wherever a defendant's denial of his obligation is punished by duplication of the damages to be recovered—as in actions under the lex Aquilia, and for the recovery of a legacy—he cannot get the money back on this plea. The older lawyers, however, applied this rule only to such legacies of specific sums of money as were given by condemnation; but by our constitution, by which we have assimilated legacies and trust bequests, we have made this duplication of damages on denial an incident of all actions for their recovery, provided the legatee or beneficiary is a church, or other holy place honoured for its devotion to religion and piety. Such legacies, although paid when not due, cannot be reclaimed.
TITLE XXVIII. OF PERSONS THROUGH WHOM WE CAN ACQUIRE OBLIGATIONS
Having thus gone through the classes of contractual and quasicontractual obligations, we must remark that rights can be acquired by you not only on your own contracts, but also on those of persons in your power—that is to say, your slaves and children. What is acquired by the contracts of your slaves becomes wholly yours; but the acquisitions of children in your power by obligations must be divided on the principle of ownership and usufruct laid down in our constitution: that is to say, of the material results of an action brought on an obligation made in favour of a son the father shall have the usufruct, though the ownership is reserved to the son himself: provided, of course, that the action is brought by the father, in accordance with the distinction drawn in our recent constitution.
1 Freemen also, and the slaves of another person, acquire for you if you possess them in good faith, but only in two cases, namely, when they acquire by their own labour, or in dealing with your property.
2 A usufructuary or usuary slave acquires under the same conditions for him who has the usufruct or use.
3 It is settled law that a slave jointly owned acquires for all his owners in the proportion of their property in him, unless he names one exclusively in a stipulation, or in the delivery of property to himself, in which case he acquires for him alone; as in the stipulation 'do you promise to convey to Titius, my master?' If it was by the direction of one of his joint owners only that he entered into a stipulation, the effect was formerly doubted; but now it has been settled by our decision that (as is said above) under such circumstances he acquires for him only who gave him the order.
TITLE XXIX. OF THE MODES IN WHICH OBLIGATIONS ARE DISCHARGED
An obligation is always extinguished by performance of what is owed, or by performance of something else with the creditor's assent. It is immaterial from whom the performance proceeds—be it the debtor himself, or some one else on his behalf: for on performance by a third person the debtor is released, whether he knows of it or not, and even when it is against his will. Performance by the debtor releases, besides himself, his sureties, and conversely performance by a surety releases, besides himself, the principal debtor.