Resources for Kesubos 21
1. The גמרא says that according to רבי each עד who says זה כתב ידי is really being מעיד on his own handwriting and not on the content of the שטר. The פּני יהושע asks why is this not an issue of דבר ולא חצי דבר? That is to say, one cannot give a half of a testimony, and yet according to רבי all each individual witness is saying is that one of the two חתימות (his own) is authentic but a שטר with one signature is not a שטר so why isn’t that a problem of חצי דבר? He answers that the ירושלמי says that a שטר with one witness is enough to be מחייב a שבועה. If so, it is not a חצי דבר. Even according to the שיטות that a שטר with one witness is not even enough to be מחייב a שבועה, that is only by a שטר with one signature, but in this case there are two signatures and the one עד is saying it’s a valid שטר with two signatures so it is certainly מחייב a שבועה. However, the נתובות המשפּט in סימן מ"ו ס"ק ו says that an עד אחד on a שטר cant be מחייב a שבועה since all the עד is saying is that there was a loan but he isn’t saying that it wasn’t paid back. The reason we assume it wasn’t paid back is because of the חזקה of שטרך בידי מאי בעי (why would I have the שטר if it was paid). However, an עד אחד can only be מחייב a שבועה when his testimony can stand on its own without the help of חזקות. (see note 3 below).
2. The חכמים says that when עדים testify that their signatures are authentic, they are really testifying on the contents of the contract being true. The רמב"ם in הלכות עדות פּרק ח׳ הל׳ א quotes this הלכה but adds that because of this, the עדים can only testify about their signatures if they remember that what is written in the contract is correct. However, if they have no recollection of the events having occurred, they cannot testify that their signatures are valid. The ש"ך in סימן מ"ו ס"ק ל"ב explains that the רמב"ם is based on the understanding that if the עדים don’t remember the testimony themselves then it is considered an עדות בכתב and would violate the principle of מפּיהם ולא מפּי כתבם. The נתובות המשפּט in סימן מ"ו ס"ק ט explains that the רמב"ם is לשיטתו that all שטרות are really only valid מדרבנן because of this issue of מפּיהם ולא מפּי כתבם. It was only a תקנת חכמים that allows us to use any שטר. The reason for the תקנה was because the עדים might die or leave town and we need some other proof that the transaction took place. Therefore, if the witnesses are standing on front of you then the חכמים did not allow you to rely on the שטר. Interestingly, the ש"ך says that even according to the רמב"ם you don’t need to ask the עדים if they remember the events of the שטר when they come to be מקיים their signatures. The רמב"ם is only discussing a case where they mentioned they don’t remember what happened.
3. The גמרא says that if a מלוה produces an unsigned שטר in the handwriting of the לוה we would be גובה מנכסים בני חורין. תוספות in ד"ה הוציא brings a מהלוקת ראשונים as to whether the לוה would be believed to say פּרעתי in this case. The שיטה that holds that one cannot say פּרעתי is straightforward-- שטרך בידי מאי בעי? However, how would we explain the שיטות that hold that even though the מלוה is believed to be מוציא ממון with this שטר, we would not apply the principle of שטרך בידי מאי בעי and one could טענה פּרעתי? The גר"ח על הש"ס says בשיטת הרמב"ם that שטרך בידי מאי בעי is never enough to be מוציא ממון on its own. The real reason a שטר works is because חז"ל gave it the power to work. But they only gave it this power on a real שטר. However, a simple כתב יד does not qualify as a שטר and one could therefore טענה פּרעתי. Interestingly, the רמב"ם in הלכות מלוה פּרק י"ד הל׳ י says that a שטר with one עד where the לוה claims פּרעתי would be valid להוציא ממון (since the עד makes it situation of מחויב שבועה ואינו יכול לישבע). The קובץ שיעורים in ב"ב תר"ב points out that based on the above it must be that the רמב"ם holds that a שטר with one עד has a דין שטר as opposed to a simple כתב יד.
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