We come now to Tractate Gittin, chapter 1, mishnah 5. The mishnah rules: "Kol get she'yesh alav ed Kuti - pasul, chutz mi'gittei nashim v'shichrurei avadim" - any document that bears the signature of a Kuti witness is invalid, except for women's divorce documents and documents freeing slaves. We should note at the outset that the word 'get' in this mishnah does not refer specifically to a divorce document for a woman, but to any type of legal document. The mishnah therefore means: any document signed by a Kuti witness is invalid.
Who were the Kutim:
The Kutim were groups of people brought by the king of Assyria into the region where the ten tribes had lived, in Samaria, and who converted to Judaism. Opinions are divided as to whether this was a valid conversion or not, and generally speaking we do not accept them; certainly after the era of the Mishnah they were no longer accepted as Jews at all, although during the era of the Mishnah there were opinions that did accept them. Our mishnah follows the view that they were valid converts, except that they had a tendency to give false testimony for financial gain, and for that reason they were not considered valid witnesses.
The reason for the distinction between divorce documents and all other documents:
The Gemara explains that in the case of women's divorce documents and documents freeing slaves, the law is that the witnesses must sign in one another's presence, and this accounts for the difference:
In divorce documents and documents freeing slaves: the second witness, apart from the Kuti, is a valid Jew, and he would not have signed after the Kuti had he had any suspicion of him. Since the Jew signed after the Kuti, he clearly knows that this particular Kuti does not lie - and therefore the document is valid.
In all other documents: there the witnesses may sign without being in one another's presence, and we must be concerned that perhaps the Jew signed first, in the second position, leaving a space above himself for someone he considered older and more distinguished than himself, and then the Kuti came and signed above him. In such a case the signature is no proof at all that the Kuti is a trustworthy person.
The opinion of Rabban Gamliel:
The Gemara points out that words are missing here in the mishnah, and at this point it should read that Rabban Gamliel disagrees with the first Tanna and says that the document is valid not only when one witness is a Kuti, but even when both witnesses are Kutim - for Rabban Gamliel held that the Kutim are accepted and trustworthy in everything relating to documents.
Documents drawn up in gentile courts:
The mishnah brings cases in which such documents are considered valid: loan documents and documents relating to sales. All of these are valid, except for divorce documents and documents freeing slaves, and the reason is this: monetary documents are nothing more than proof, and if they were drawn up in the official courts of the gentiles we assume that they were done honestly and that the witnesses were fit. But a divorce document and a document freeing a slave - the documents themselves are what bring about the halachic change: they create the divorce, and they grant freedom to a gentile slave who now becomes a Jew. Documents that carry halachic force and do not serve merely as evidence are not valid unless they were drawn up and signed by Jews.
The approach of Reish Lakish:
Reish Lakish said that these documents of women's divorce and freeing of slaves are valid even if they were drawn up with gentile signatures. His reasoning is that Reish Lakish held like Rabbi Eliezer, that the witnesses to the delivery - the witnesses who testify to the handing over of the get from the husband to the wife - are the essential witnesses, while the signing witnesses are not the essential element, and therefore it is sufficient even though they are not valid witnesses.
Reish Lakish said further that the idea of disqualifying gentile witnesses was mentioned only where the document was drawn up by a layman - that is, only where it was drawn up by gentiles in a setting that is not a court, outside the official court system. In such a case there is room for concern even in documents of sale and of loan, that perhaps the signatures of these gentiles are not trustworthy, since they were not made in the official courts.
In summary: we learned that a document signed by a Kuti witness is invalid, except for women's divorce documents and documents freeing slaves - where the fact that the witnesses signed in one another's presence proves that the Jewish witness relied on the Kuti. We saw the opinion of Rabban Gamliel, who validates even when both witnesses are Kutim, the distinction between monetary documents that serve merely as evidence and a divorce document or document freeing a slave that bring about a halachic change, and the approach of Reish Lakish, that the witnesses to the delivery are the essential ones, and that the disqualification was stated specifically regarding a document drawn up outside the official courts.