[POMPONIUS libro quinto decimo ad Sabinum. ] §18.5.1.prCelsus filius putabat, si uendidisset mihi filius familias rem peculiarem, etiam, si conueniat ut abeatur ab ea uenditione, inter patrem et filium et me conuenire debere, ne, si cum patre solo pactus sim, filius non possit liberari et quaeratur, utrumne nihil agatur ex ea pactione an uero ego quidem liberer, filius maneat obligatus, sicuti, si pupillus sine tutoris auctoritate paciscatur, ipse quidem liberatur, non etiam qui cum eo pactus est.
[POMPONIUS, Book 15 on Sabinus.] Celsus the son used to think that, if a filius familias had sold me a thing belonging to his peculium, even if it is agreed to withdraw from that sale, an agreement ought to be made between the father, the son, and me, lest, if I should make an agreement with the father alone, the son could not be released and it be asked whether nothing is effected by that agreement or, on the other hand, I indeed am released while the son remains bound; just as, if a pupillus should make an agreement without the authority of his tutor, he himself indeed is released, but not also the person who made the agreement with him.
nam quod Aristo dixit posse ita pacisci, ut unus maneat obligatus, non est uerum, quia pro una parte contrahentium abiri pacto ab emptione non possit: et ideo si ab una parte renouatus sit contractus, dicitur non ualere eiusmodi pactionem.
For what Aristo said, that it is possible to agree in such a way that only one remains bound, is not true, because it is not possible to withdraw from a sale by agreement for the benefit of only one party to the contract: and therefore, if the contract has been renewed on one side only, it is said that an agreement of this kind is not valid.
sed dicendum est patre paciscente et liberato aduersario filium quoque obiter liberari.
But it must be said that when the father makes the agreement and the adversary is released, the son also is released incidentally.