[PAULUS libro decimo quaestionum. ] §45.1.128.prSi duo rei stipulandi ita extitissent, ut alter utiliter, alter inutiliter stipularetur, ei, qui non habet promissorem obligatum, non recte soluitur, quia non alterius nomine ei soluitur, sed suae obligationis, quae nulla est.
[PAULUS, Questions, book 10.] two joint stipulators should stand in such a position that one stipulates validly and the other invalidly, payment is not validly made to the one who does not have the promisor bound to him, because payment is made to him not in the name of the other, but in the name of his own obligation, which is null.
eadem ratione qui Stichum aut Pamphilum stipulatur, si in unum constiterit obligatio, quia alter stipulatoris erat, etiamsi desierit eius esse, non recte soluitur, quia utraque res ad obligationem ponitur, non ad solutionem.
By the same reasoning, if someone stipulates for Stichus or Pamphilus, and the obligation is established on one of them only because the other belonged to the stipulator, even if it has ceased to belong to him, payment [of the latter] is not validly made, because both things are set down for the purpose of the obligation, not for the purpose of the payment.