Commentary for Bava Metzia 67:11

איכא דאמרי אמר רב פפא שואל נמי כיון שאמר הריני משלם מקני ליה כפילא דאי בעי פטר נפשיה במתה מחמת מלאכה אמר ליה רב זביד הכי אמר אביי שואל עד שישלם מאי טעמא הואיל וכל הנאה שלו בדיבורא לא מקני ליה כפילא

R. Papa said: If a gratuitous bailee merely says, 'I was negligent,' he [the bailor] assigns the twofold repayment to him, since he could have freed himself by [the plea of] theft. If a paid bailee merely says, 'It was stolen', the twofold repayment is made over to him, since he could, if he wished, have freed himself by pleading that it was hurt or had died. But if a borrower says, 'I will pay,' he [the bailor] does not assign him the twofold repayment; for how could he have freed himself? By [the plea], it died on account of its work? That is a rare occurrence.<span class="x" onmousemove="('comment',' Hence a palpable lie, which one does not care to state. ');">¹⁰</span>

Maharam Schiff on Bava Metzia