[MARCIANUS libro tertio regularum. ] §19.5.25.prSi operas fabriles quis serui uice mutua dedisset, ut totidem reciperet, posse eum praescriptis uerbis agere, sicuti si paenulas dedisset, ut tunicas acciperet: nec esse hoc contrarium, quod, si per errorem operae indebitae datae sunt, ipsae repeti non possunt.
[MARCIANUS, in the third book of Rules.] If anyone should have given the artisan services of a slave in mutual exchange, in order to receive just as many in return, he can bring an action with prescribed words, just as if he had given cloaks in order to receive tunics; nor is this contradicted by the fact that, if undue services have been given by mistake, they themselves cannot be recovered.
nam aliud dando, ut aliud reddatur, obligari iure gentium possumus: quod autem indebitum datur, aut ipsum repeti debet aut tantundem ex eodem genere, quorum neutro modo operae repeti possunt.
For by giving one thing so that another may be returned, we can become obligated under the law of nations; but when what is not due is given, either the thing itself ought to be recovered or the equivalent of the same kind, in neither of which ways can services be recovered.