Bava Metzia, page 12 side b, page 13 side a, and page 16. Rambam, Laws of Loans, chapter 23, law 5. Shulchan Aruch, Choshen Mishpat ch 39 law 13, ch 65

I was thinking about the idea of Rav Shach in laws of loans 23:5 and it occurred to me that what he is saying is based on an idea I recall from Bava Metzia the end of the 9th chapter that if you hire someone and the day is finished that you have only the whole night to pay him. after that you transgresses prohibition of the Torah, and therefore it is assumed that you paid him on time. -- Just to make it clear what I am saying and what I think rav Shach is saying let me bring here the basic idea at hand. The Rif holds if there is a document testifying that there was (or there is?) a loan, that the lender has to make the loan, if he has not done so yet. The Rashba disagrees. Also, the Rif holds a document testifying there was a loan, it has no validity until it reaches the hands of the lender and the Rashba disagrees. Rav shach says that each opinion depends on the other. Now the law is that if one finds a document in the street testifying there was a loan one must return it to the lender. (I should add that in general when there is a worry if a document is found in the street that the worry is that it fell from the borrower, not the lender.) So to the Rif, why return the document to the lender? It must be because once it was written, and there was a kinyan sudar (acquisition by means of exchange of a handkerchief), that the lender is required to make the loan and my point is that therefore we assume that he did based on the general in hamekabel chapter 9. The reasoning is that the kinyan sudar is not kinyan cesef (acquisition by means of exchange of moeny) so we assume the actual loan was made even if the document did not reach the lender, but just by the fact of the kinyan sudar.(Or the we assume the document did reach the lender? Maybe. But that does not seem to be the general worry about a document that fell. we assume it fell from the borrower because it might not be valid so he was not careful about keeping it safe.)-- However, the Rashba disagree with all this, and holds there is not obligation to make the loan, just like the borrower can also say at the last minute that he does not need the money an doe not want the loan. But he also holds the documents valid even before it reaches the lender because he decided the law like Abyee that the witnesses make the document valid the minute they sign or testify verbally. However, the fact that the document is valid does not make an obligation to make the loan since it is a kinyan sudat, not kinyan kesef. ----------------------------------------------------------------I was thinking about the idea of רב שך in laws of loans 23:5and it occurred to me that what he is saying is based on an idea I recall from בבא מציעא the end of the פרק טשיעי that if you hire someone and the day is finished that you have only the whole night to pay him. after that you transgresses prohibition of the לאו, and therefore it is assumed that you paid him on time. -- Just to make it ברור what I am saying and what I think רב שך is saying let me bring here the basic idea at hand. The ר’’ף holds if there is a document testifying that there was (or there is?) a loan, that the מלווה has to make the loan, if he has not done so yet. The רשב’’א disagrees. Also, the ר’’ף holds a document testifying there was a loan, it has no validity until it reaches the hands of the מלווה and the רשב’’א disagrees. רב שך says that each opinion depends on the other. Now the law is that if one finds a document in the street testifying there was a loan one must return it to the מלווה. (I should add that in general when there is a worry if a document is found in the street that the worry is that it fell from the לווה, not the מלווה.) So to the ר’’ף, why return the document to the מלווה? It must be because once it was written, and there was a קניין סודר (acquisition by means of exchange of a handkerchief), that the מלווה is required to make the loan and my point is that therefore we assume that he did based on the general כלל principle in המקבל פרק טThe reasoning is that the קניין סודר is not קנין כסף (acquisition by means of exchange of money) so we assume the actual loan was made even if the document did not reach the מלווה, but just by the fact of the קניין סודר.(Or the we assume the document did reach the מלווה? Maybe. But that does not seem to be the general worry about a document that fell. we assume it fell from the לווה because it might not be valid so he was not careful about keeping it safe.)-- However, the רשב’’א disagree with all this, and holds there is not obligation to make the loan, just like the לווה can also say at the last minute that he does not need the money an doe not want the loan. But he also holds the documents valid even before it reaches the מלווה because he decided the law like אביי that the witnesses make the document valid the minute they sign or testify verbally. However, the fact that the document is valid does not make an obligation to make the loan since it is a קניין סודר, not קנין כסף.