Bava Basra, chapter 10, Mishnah 2. This Mishnah includes a series of halachos concerning documents. The first halachah continues the topic of the previous Mishnah: the differences between a tied document and a simple document.
The number of witnesses for a simple document and a tied document:
"Get pashut edav bishnayim" - for a standard document, two witnesses signed on it are sufficient.
"Umekushar bishloshah" - a tied document requires a minimum of three signatories. The underlying rule is that there must be one signatory for every fold in the document, so if there are ten folds, ten signatories are required; three is the minimum.
"Pashut shekasav bo eid echad, umekushar shekasav bo shenei eidim - sheneihem pesulin" - in both these cases, the document is completely invalid. It is obvious that one witness is insufficient, but the true novelty is regarding a tied document with two witnesses: on a Torah level, this would be a valid document, yet nonetheless, since the Sages established that a tied document requires a minimum of three, their authority prevails and they invalidate the document.
Contradictions between amounts in the document:
From here, the Mishnah moves on to discuss contradictions in the text of the document. "Kasav bo zuzin me'ah de'inun sela'in esrin" - a loan document stating that the loan stands at a hundred zuz, which are twenty sela'im. A sela is generally worth four zuz, meaning a hundred zuz are twenty-five sela'im, while twenty sela'im are only eighty zuz. If so, which amount is binding? The Mishnah rules: "Eino ela esrin" - the lender collects only the lower amount, the twenty sela'im, which are eighty zuz.
It is worth pausing here on an important point: this is a situation where the two descriptions can be reconciled with one another. It is possible that it refers to zuz of low quality, as the coins were made of silver and wore down over time; when the silver wore down, or the stamp minted on the coin eroded making it less acceptable in stores, its actual value dropped. Therefore, it is reasonable to say that twenty standard sela'im are worth a hundred worn out and lower quality zuz.
Similarly: "Zuzin me'ah de'inun tlasin sela'in" - the document states a hundred zuz which are thirty sela'im. Here too, a hundred zuz should be twenty-five sela'im, and thirty sela'im are generally a hundred and twenty zuz; but it is possible that it refers to worn out and lower quality sela'im. Therefore, "Eino ela maneh" - a "maneh" is a hundred zuz, or a hundred dinars. This is the rule in all these cases: the lender collects the lesser of the two amounts.
A document where the number of coins was erased:
"Keseph zuzin de'inun venimchak" - the document stated silver coins to the number of, but the number itself was erased, and it is unknown how many coins were lent. "Ein pachus mishnayim" - since "zuzin" is written in the plural, and the minimum plural is two, this is all the lender can collect.
"Keseph sela'in de'inun venimchak" - it states silver sela'im, which are larger coins, and their number was erased. Here too, "ein pachus mishnayim", since "sela'im" is plural.
"Darkonos de'inun venimchak" - darkonos are valuable Persian gold coins, mentioned in the verses in the Book of Ezra, and we have already discussed them in Tractate Sukkah. Even though these are very large coins, the halachah is the same: "Ein pachus mishtayim" - he collects two, since it is plural.
A contradiction between the beginning of the document and its body:
"Kasav bo milmalah maneh umilmatah masayim, milmalah masayim umilmatah maneh" - here it is an irreconcilable contradiction, unlike the previous cases where it could be attributed to lower quality zuz or sela'im. At the beginning of the document it was written, for example, that Reuven is asking to borrow a maneh from Shimon, while further on, in the body of the document detailing what, where, and how the debt will be repaid, it states two hundred; or vice versa: two hundred at the beginning and a maneh in the details.
In this case, we do not follow the lesser of the two amounts. Instead, we assume that the second mention is intended to convey the details precisely, while the first is mistaken. Therefore, "hakol holech achar hatachton" - everything follows the lower one - we follow the mention that appears below. This does not mean something written literally on the very last line, because there we might suspect that someone added it in order to alter the document. Rather, when the body of the document specifies an amount different from what was written in the opening description, we follow the body of the document, assume it is correct, and amend everything stated before it accordingly.
"Im kein, lamah kosvin es ha'elyon?" - If so, why do they write the upper one?
What is the point of writing the amount at the top if we ignore it anyway? The Mishnah answers: "she'im timachek os achas min hatachton - yilmad min ha'elyon" - that if one letter is erased from the lower one, it can be learned from the upper one. If a single letter was erased from the details in the body of the document, we can deduce from what is written above what the missing letter was. This restoration is permitted for one letter only, out of concern that if more than one letter were filled in, it would be possible to change the meaning of entire words; however, a single letter that was erased - we can determine what it was from the text written above.