[IDEM libro decimo ad edictum. ] §22.1.37.prEt in contraria negotiorum gestorum actione usurae ueniunt, si mutuatus sum pecuniam, ut creditorem tuum absoluam, quia aut in possessionem mittendus erat bonorum tuorum aut pignora uenditurus.
[THE SAME, in his tenth book on the Edict.] Interest is also allowed in the counter-action for unauthorized agency, if I have borrowed money in order to discharge your creditor, because he was either about to be put into possession of your goods or was going to sell your pledges.
quid si domi habens propter eandem causam solui? puto uerum, si liberaui ex magno incommodo, debere dici usuras uenire, eas autem, quae in regione frequentantur, ut est in bonae fidei iudiciis constitutum: sed si mutuatus dedi, hae uenient usurae quas ipse pendo, utique si plus tibi praestarim commodi, quam usurae istae colligunt.
What if I, having money at home, paid it for the same reason? I think it is correct to say that interest should be allowed, provided that I released you from a great disadvantage; but this is the interest which is customary in the region, as has been established in actions of good faith. But if I borrowed and paid, that interest will be allowed which I myself pay, provided at all events that I have conferred more benefit on you than those interest payments amount to.