[POMPONIUS libro tertio ex Plautio. ] §45.1.90.prCum stipulati sumus pro usuris legitimis poenam in singulos menses, si sors soluta non sit, etiamsi sortis obligatio in iudicium sit deducta, adhuc tamen poena crescit, quia uerum est solutam pecuniam non esse.
[POMPONIUS, On Plautius, Book 3] When we have stipulated, in place of legal interest, for a penalty per month if the principal should not be paid, even if the obligation of the principal has been brought into court, the penalty nevertheless still increases, because it remains true that the money has not been paid.