Reference for Bava Metzia 69:7
ומאי שנא לוה דמהימן ליה למלוה ומאי שנא מלוה דלא מהימן ליה ללוה לוה מקיים ביה במלוה (משלי יא, ג) תומת ישרים תנחם מלוה מקיים ביה בלוה (משלי יא, ג) וסלף בוגדים ישדם:
Then let the debtor believe the creditor in this too [viz.,] how much it was worth! — [The debtor reasons,] he [the creditor] did not fully ascertain it [sc. the value]. Then let the creditor believe the debtor, since he does fully know it? — [Nevertheless,] he does not believe him. Wherein lies the difference, that the debtor believes the creditor, but not vice versa? — The debtor applies to the creditor, <i>The integrity of the upright shall guide them</i>:<span class="x" onmousemove="('comment',' Prov. XI, 3; i.e., he assumes that the creditor's prosperity proves his trustworthiness. ');"><sup>5</sup></span>