[GAIUS libro tertio de uerborum obligationibus. ] §3.5.38.prSoluendo quisque pro alio licet inuito et ignorante liberat eum: quod autem alicui debetur, alius sine uoluntate eius non potest iure exigere.
[GAIUS, On Verbal Obligations, Book III] Anyone, by paying on behalf of another, even if that person is unwilling and ignorant, releases him; however, what is owed to someone, another cannot legally demand without his consent.
naturalis enim simul et ciuilis ratio suasit alienam condicionem meliorem quidem etiam ignorantis et inuiti nos facere posse, deteriorem non posse.
For both natural and civil reason have suggested that we can indeed make another's condition better, even if he is ignorant and unwilling, but we cannot make it worse.