א דין שלישות. ובו ז סעיפים: שליש בזמן ששלישותו בידו נאמן כשני עדים אפי' אם הוא קרוב ואין צריך לישבע: הגה ואפי' כתבו ענין השלישות בשטר לא נאמר שלא סמכו על ענין השליש אלא גם בזה השליש נאמן (ב"י בשם הרשב"א) ואע"פ שעבר הזמן שהיה לו להחזירו לאחד (מהן) ולא החזיר עדיין שליש הוא ונאמן ואפילו הכחישו אחד מהם ואמר שלא עשאו שליש השליש נאמן ואפי' הכחישו שניהם השליש נאמן והוא שלא יהיה ביניהם ובין השליש הכחשה בסך המעות שבידו דא"כ הו"ל נוגע בדבר ואינו נאמן: הגה במקום שאין לו מיגו אבל במקום שיש לו מיגו נאמן (מרדכי פ' החובל) ויכולים להשביעו אפי' בטענת שמא (הגהות מרדכי דגטין) שטר שהיה ביד שליש והוציאו מתחת ידו בב"ד ואמר פרוע הוא אע"פ שהשטר מקויים נאמן שאילו רצה היה שורפו או קורעו וכן אם מת השליש ונמצא כתב יוצא מתחת ידי השליש ששטר זה המונח אצלו פרוע הוא (ה"ז פרוע) אע"פ שאין עדים על הכתב (וע"ל סי' ס"ה מדינים אלו) אבל כתב שיצא מתחת ידי המלוה ששטר פלוני פרוע אפי' היה בכתב ידי המלוה אינו אלא כמשחק (התובע ישלם שכר השלישות) (הגהות מרדכי ס"פ ז"ב):
1 Laws of a Third Party, 7 Seifim: A third party, so long as he has the item that was given to him in his possession, is believed as if there were two witnesses, even if he is related. He is not required to take an oath. Rema: Even if the handing over to the third party was written in a document, we do not say that they are not relying on the concept of a third party. Rather, here too the third party would be believed. (Beis Yosef in the name of the Rashba) Even if the timeframe given to hand over the document has passed and the third party has not given the document, he still is a third party and he is believed. The third party is believed even if one of the parties contradicts him and says he never made him a third party. The third party is even believed where both parties contradict him so long as there is no dispute between the parties and the third party regarding the amount of money in his possession, because otherwise the third party would have a stake in the matter and would not be believed Rema: In a case where the third party does not have a migu. If, however, the third party has a migu, he is believed. (Mordechai, Perek 'HaChovel') [Ed. Note: A migu is a reason that a claim that would otherwise be rejected by a Jewish civil court should be accepted based on the fact that the litigant could have prevailed in the case based on a different claim were he disposed to lie. To be effective, the logic underlying the migu must be impeccable and there are a variety of cases in which the Migu argument is invalid.] The parties may force him to swear, even with an uncertain claim. (Hagahos Mordechai, Gitin) If the third party had the document, produced it in court and says it was paid back, he would be believed even if the document was verified because had he wanted he could have burnt or torn the document. Similarly, if the third party died and a writing was discovered in the third party’s possession saying the document that he had was paid back, the document is considered paid back even if there are no witnesses on the writing. (See later Siman 65 with respect to these laws). If, however, a writing was produced from the lender’s possession saying that so and so’s document was paid back, it is treated as a joke, even if it was written in the lender’s handwriting. (The plaintiff must pay the expenses of the third party). (Hagahos Mordechai)