The Rav Joseph Karo (author of the Shulchan Aruch) writes that witnesses need to testify verbally, not by writing (Choshen Mishpat chapter 28, law 11). But to validate a document, in choshen mishpat chapter 46 law 7 the Rema says one can testify by writing in the name of the Rivash (Izhak ben Sheshet). And yet later on when the Shulchan Aruch writes (chapter 46 law 36)if one is a witness, and then suddenly became unable to speak , he cannot testify as for the validity of his signature (even by writing). And the Rema does not disagree there. Why? Rav Shmuel Rozovski [Rosh yeshiva of Ponovitch before Rav Shach] is this. Rav Joseph Karo holds like Tosphot that a document with only one witness does not have a valid category of a document, and therefore to validate it, one needs to testify verbally, not in writing. This seems to imply that Rav Karo holds a document written against the consent of the borrower is also not considered to be a document, and therefore there also one must testify for it’s validity verbally, while the Rema holds one can testify in writing about its validity. It seemed to me at first hard to understand what Rav Shmuel means by a document having validity and yet still needing to be validated. He does not explain what he mean exactly. However, it occurred to me that he must hold that the Shulchan Aruch Rav Karo holds like the Rambam that no document is valid from the law of the Torah, only the words of the sages makes documents of loans valid at all. But even then, one needs to validate them when the lender comes to court to collect his payment. Therefore one must always testify for the validity of a document verbally because the verse from their mouth which implies not from their writing. However the Rema must hold that documents of loans and business are valid from the Torah. Since they are already valid, then one can testify as for their validity in writing. Only when a document was written against with only one witness, then it has no validity from the Torah, so one has to testify as for its validity from the words of the sages verbally. This argument between the Shulchan Aruch and the Rema is based on Tosphot Ketuboth page 20.One opinion is a document written without consent of the borrower does not have the status of a document, and Rav Karo agrees with this, and the Rema disagrees. Another opinion is a document with only one witness does not have the status of a document. Both the Shulchan Aruch and the Rema agree. ------------------------------------------------------------------------------------------------------------------------------------- The שלחן ערוך writes that witnesses need to testify verbally, not by writing (חושן משפט פרק כ''ח ס''ק י''א ). But to validate a document, in חושן משפט סימן מ''ו סעיף ז' the רמ''א says one can testify by writing in the name of the ריב''ש (יצחק בן ששת). And yet later on when the שלחן ערוך writes (chapter מ''ו lawל''ו ) if one is a witness, and then suddenly became unable to speak , he cannot testify as for the validity of his signature (even by writing). And the רמ''א does not disagree there. Why? the רב שמואל רוזובסקי is this. רב יוסף קרו holds like תוספות that a document with only one witness does not have a valid category of a document, and therefore to validate it, one needs to testify verbally, not in writing. This seems to imply that רב קרו holds a document written against the consent of the borrower is also not considered to be a document, and therefore there also one must testify for it’s validity verbally, while the רמ''א holds one can testify in writing about its validity. ----It seemed to me at first hard to understand what רב שמואל means by a document having validity and yet still needing to be validated. He does not explain what he mean exactly. However, it occurred to me that he must hold that the שלחן ערוךholds like the רמב''ם that no document is valid from the law of the תורה, only the words of the סופרים makes documents of loans valid at all. But even then, one needs to validate them when the lender comes to court to collect his payment. Therefore, one must always testify for the validity of a document verbally because the verse "מפיהם" which implies ולא מפי כתבם. However, the רמ''א must hold that documents of loans and business are valid from the תורה. Since they are already valid, then one can testify as for their validity in writing. Only when a document was written against with only עד אחד, then it has no validity from the תורה, so one has to testify as for its validity from the words of the סופרים verbally. This argument between the שלחן ערוך and the רמ''א is based on תוספות כתובות page כ''. One opinion is a שטר written without consent of the borrower does not have the status of a document and רב קרו agrees with this and the רמ''א disagrees. Another opinion is a document with only one witness does not have the status of a document. Both the שלחן ערוך and the רמ''א agree.